WorldMags.net Vol. XV
No. 2
February 2013
Corporate Office: Plot 99, Sector 44 Institutional Area, Gurgaon -122 003 (HR), Tel : 0124-4951200 e-mail :
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Managing Editor : Editor :
Mahabir Singh Anil Ahlawat
Contents
Xplore & Win Contest
4
CBSE Board Sample Paper 2013
6
Assertion & Reason
14
NEET Practice Paper 2013
19
High Yield Facts – Botany Ecological Succession
27
35
PMT Essential Blood and Hemostasis
49
High Yield Facts – Zoology Common Human Diseases-II
61
NCERT Xtract Questions for NEET
69
Quick PMT Revision Organisms & Population-III Xplore & Win Solutions (Nov.)
73
NEET Special Biotechnology
74
Owned, Printed and Published by Mahabir Singh from 406, Taj Apartment, New Delhi - 29 and printed by Personal Graphics and Advertisers (P) Ltd., Okhla Industrial Area, Phase-II, New Delhi. Readers are adviced to make appropriate thorough enquiries before acting upon any advertisements published in this magazine. Focus/Infocus features are marketing incentives MTG does not vouch or subscribe to the claims and representations made by advertisers. All disputes are subject to Delhi jurisdiction only. Editor : Anil Ahlawat Copyright© MTG Learning Media (P) Ltd. All rights reserved. Reproduction in any form is prohibited.
A miracle in medical research
P
rofessor Robert Maclaren and his group in the University of Oxford have developed a method of giving sight to the born blind. The research was performed on mice that had no photoreceptions in their retinas. The result is they cannot distinguish between night and day or light and darkness. The scientists injected light sensing cells into the eye and two weeks after the injection, a retina has been formed. This was curing a case of a complete lack of retina. Previous studies had successfully treated partially degenerated retinas. After the development of the new retina, not only the mice showed constriction of pupils when irradiated with light, but also studies on their brain showed that the visual information was being processed by the brain. According to Pete Coffee from the Institute of Ophthalmology at the University of London, the finding were important as the studies looked at most clinically relevant and severe cases of blindness however, he said this and similar studies needed to show how good the recovered vision was as brain scans and tests of light sensitivity were not enough. Loss of sight due to various injuries and blindness since birth or after suffering a serious disease like small-pox all can be corrected by this method. Replacing heart valves, insertion of pacemakers, grafting in liver and treating rheumatism and weakness of bones by modern techniques are being practiced in India in many of our hospitals. Every single technique or discovery in any part of the world is also an asset to every country in the world. Whether is research on radioactive materials or in information technology, they are the collective wealth of the world. Any discovery in any part of the world will be available in every city, thanks to the Informatic Explosion. Research and Publication- are the right hand and the left hand of progress.
Anil Ahlawat Editor
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Dear Readers, The purpose of this Xplore & Win is to develop curiosity in you about the biological concepts and to give you an opportunity to learn in investigative manner. This will connect the biological concepts with their applications in real world and will put interesting-to-search queries. Q1. Why melatonin is referred to as “sleep hormone”?
Q6. Give an example of induced succession.
Refer : Assertion and Reason – Endocrine system.
Q2. How restriction modification system in bacteria functions as a part of defense mechanism against bacteriophages infection? Refer : NEET Special – Biotechnology.
Refer : High Yield Facts – Ecological Succession.
Q7. Why men have higher hematocrit than women? Explain.
Refer : PMT Essential – Blood and Hemostasis.
Q8. What is the rate-limiting factor in blood coagulation cascade?
Q3. Why gout sufferers should avoid consuming meat, particularly liver, kidney, brain, thymus gland and other glands?
Q9. Which evolutionary force is believed to be the driving force
Refer : High Yield Facts – Common Human Diseases-II.
behind sympatric speciation?
Q4. What are two forms of diabetes mellitus?
Refer : PMT Essential – Blood and Hemostasis.
Refer : High Yield Facts – Common Human Diseases-II.
Refer : CBSE Board – Sample Paper.
Q5. Climax community has maximum diversity and niche specialization. Justify.
Q10. During expiration, how is the pressure gradient formed
Refer : High Yield Facts – Ecological Succession.
between the lungs and the atmosphere? Refer : Concept Map - Breathing and Respiration.
Note : ‘xplore’ also serves as Quiz which is open for the Readers to solve. You can send in your answers to us either through e-mail or by post and, Reader with more correct answers will be rewarded with exciting prize.
Your feedback will help us to serve you better
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We request Readers to send their views/suggestions. The honest feedback given by you will help in improvement of your favourite magazine. E-mail your suggestions to :
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GENERAL INSTRUCTIONS (i) All questions are compulsory. (ii) The question paper consists of four sections A, B, C and D. Section-A contains 8 questions of 1 mark each, Section B is of 10 questions of 2 marks each, Section C is of 9 questions of 3 marks each whereas Section D is of 3 questions of 5 marks each. (iii) There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and all the three questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions. (iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
SECTION - A 1. Mention any four asexual reproductive structures that is found among different groups of organisms. 2. Compatibility reaction is determined by special proteins X and Y, X being present over zona pellucida and Y is over sperm surface. What are X and Y? 3. In 1928, after a series of experiments with Streptococcus pneumoniae, Frederick Griffith concluded that some ‘transforming principle’, transferred from the heat-killed S-strain had enabled the R-strain to synthesize. A smooth polysaccaride coat and to become virulent. What is this ‘transforming principle’? 4. Compare male heterogamety and female heterogamety. 5. Which lymphoid tissue constitutes about 50 per cent of the lymphoid tissue in human body? 6. Give an example of crop which is produced by mutation breeding method. 7. Which novel strategy is being adopted to prevent nematode infestation in dicot plants? 8. Out of every 10 animals on Earth, 7 are ______. (a) mammals (b) crustaceans (c) molluscs (d) insects.
SECTION - B 9. Evolution is a stochastic process based on chance events in nature and chance mutation in the organisms. Justify. 6
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10. Differentiate between flowers of bringal and beans. 11. Study the given graph and answer the questions that follows.
(i) Name the hormones X, Y and Z. (ii) The presence of which of these hormones (X, Y or Z) in urine helps in detecting pregnancy? 12. List any four objectives that you would recommend for biofortification. 13. Trace the development of microsporocyte in the anther to a mature pollen grain. 14. Why organs for transplantation cannot be taken from just anybody? 15. Give the scientific names for the following: (i) The joining of genes, set of genes or parts of genes, into new combinations, either biologically or through laboratory manipulation.
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(ii) An independent, stable, self replicating piece of DNA in a bacterial cell that is not a part of the normal cell genome and that never becomes integrated into the host chromosome. (iii) A small segment of DNA that binds to a complementary strand of DNA. (iv) A technique used for introducing a solution of DNA into a cell using a fine microcapillary pipette. 16. Represent diagrammatically the formation and joining of sticky ends of DNA. 17. Refer the given figure to answer the questions that follow.
(i) What is X? (ii) Why is X important for molecular geneticists? 18. State the differences between intraspecific and interspecific competition. OR Why secondary succession is faster than primary succession?
SECTION - C
19. Which type of natural selection is believed to be the driving force behind the sympatric speciation? Explain. 20. What is gametogenesis? Name its two types and give differences between them. 21. (i) In which of these seeds, endosperm is persistent? Wheat, Rice, Barley, Pea, Bean, Palm. (ii) Write down the fate of endosperm. 22. In a large population, only a person in 10,000 is albino. What will be the frequency of carriers of albinism in the population? 23. Refer the given figure of lac operon and answer the questions that follow.
(i) When the i-gene is constitutively expressed, then substance labelled ‘X’ will be inducer or inhibitor? Explain. (ii) The z gene has undergone nonsense mutation. What would be the possible consequences of this? 24. Fill in the blanks in the given table. Disease
Pathogen
Vector
Symptoms
—
Entamoeba histolytica
Malaria
Plasmodium Anopheles —
African sleeping sickness
—
Glossina palpalis
Recurrent fever, anaemia, patient falls asleep.
Kalaazar or Dumdum fever
—
—
High fever, spleen enlargement, anaemia, darkening of skin.
—
Abdominal pain, diarrhoea, blood in faeces.
OR (i) Mention the property that enables the explants to regenerate into a new plant. (ii) A banana herb is virus-infected. Describe the method that will help in obtaining healthy banana plants from this diseased plant. 25. The cloning vector pBR322 has two antibiotic resistance genes: ampicillin and tetracycline. This is because one antibiotic resistance gene helps in selecting the transformants, whereas the other antibiotic resistance gene helps in selection of recombinants. Explain. 26. In winter, storms have brought nutrient-rich water into a lake. Based on the data on the population of unicellular algae in the lake throughout the year, the given graph is plotted.
(i) What term is given to the condition occurring in summer months? (ii) Suggest possible conditions that you would observer between May to September. 27. Describe in detail the species area relationship as given by Alexander von Humboldt.
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28. A dihybrid heterozygous round yellow seeded garden pea (Pisum sativum) offspring was crossed with a double recessive parent : (i) What type of the cross is this ? (ii) Work out the genotype and phenotype of the progeny. (iii) What principle of Mendel is illustrated through the result of this cross ? OR In what way did Lederberg’s experiment provide a clear support to Darwinian view point of selection?.
29. Discuss the causes and effects of global warming. What measures need to be taken to control global warming? OR (i) What is photochemical smog composed of? How does this affect the plants? (ii) Mention the consequences of deforestation. *30. A farmer is struggling to grow vegetables and crops in his field. He has applied many available fertilizers to improve the fertility of the field, but this has shown opposite effect, the field has become barren due to overuse of fertilizers. (i) Do you think, the farmer must know the webs of interaction between the myriad of organisms that constitute the flora and fauna of the field? (ii) What changes in agricultural practices would you suggest him?
SOLUTIONS 1. Zoospores (Chlamydomonas), conidia (Penicillium), buds (Hydra) and gemmules (sponge). 2. X - Fertilizin; Y - Antifertilizin. 3. DNA is the transforming principle. 4. Comparison of male heterogamety and female heterogamety is as follows: Male heterogamety 1. Male produces two different types of gametes: (a) either with or without X-chromosome or (b) some gametes with X-chromosome and some with Y-chromosome.
Female heterogamety Female produces two types of gametes either with Z or with W chromosome.
2. Examples, Drosophila, human, etc. Example, birds. 5. Mucosa associated lymphoid tissue (MALT). 6. Sharbati Sonora or Pusa Lerma. 7. RNA interference (RNAi). 8. (d) Insects. 8
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9. Excess use of herbicides, pesticides, etc., has only resulted in selection of resistant varieties in a much lesser time scale. This is also true for microbes against which we employ antibiotics or drugs against eukaryotic organisms/ cell. Hence, resistant organisms/cells are appearing in a time scale of months or years and not centuries. These are examples of evolution by anthropogenic action. This also tells us that evolution is not a directed process in the sense of determinism. It is a stochastic process based on chance events in nature and chance mutation in the organisms. 10. Differences between flower of brinjal and beans are as follows : Flower of brinjal (Chasmogamous flower) 1. Open flowers with exposed anthers and stigma and these flowers are similar to the flowers of other species. 2. Require agents.
Flower of beans (Cleistogamous flower) Closed flowers in which anthers and stigma lie close to each other and anthers dehisce within flower buds.
pollinating Do not require pollinating agents.
3. These flowers favour cross These flowers ensure self pollination. pollination. 11. (i)
X - Human chorionic gonadotropin (HCG) Y - Oestrogen Z - Progesterone
(ii) X - HCG. 12. Biofortification is the method of breeding crops with higher levels of vitamins and minerals or higher proteins and healthier fats in the view to improve public health.
Four objectives of biofortification are to unprove (i) Protein content and quality (ii) Oil content and quality (iii) Vitamin content (iv) Micronutrient and mineral content.
13. In an anther, each cell of the sporogenous tissue is a potential pollen or microspore mother cell (PMC). Each PMC divides by meiosis to form a microspore tetrad. This process is called microsporogenesis. As the anthers mature and dehydrate, the microspores dissociate from each other and develop into pollen grains. The hard outer layer called the exine is made up of sporopollenin. The inner wall of the pollen grain is called the intine. When the pollen grain is mature it contains two cells, the vegetative cells and generative cell. * Value based question
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WorldMags.net 17. (i) X - Ti plasmid.
14. Success for transplantation depends on the degree of compatibility between donor and graft. Grafts from just any source - an animal, another primate, or any human beings cannot be made since the grafts would be rejected sooner or later. Tissue matching, blood group matching are essential before undertaking any graft/transplant and even after this the patient has to take immuno-suppresants all his/her life. The body is able to differentiate ‘self’ and ‘nonself’ and the cell-mediated immune response is responsible for the graft rejection.
The success of tissue and organ transplants depends on the donor’s and recipient’s human leucocyte antigens (HLA) encoded by the HLA genes. These proteins are alloantigens; i.e, they differ among members of the same species. If the HLA proteins on the donor’s cells differ from those on the recipient’s cells, an immune response occurs in the recipient. The genes for the HLA proteins are clustered in the major histocompatibility complex (MHC), located on the short arm of chromosome 6.
(ii) Agrobacterium tumifaciens is a soil-inhabiting bacterium that may invade growing plants at the junction of root and stem, where it can cause a cancerous growth known as a crown gall. The bacterium, which infects dicotyledonous plants only, contains plasmid (known as a Ti plasmid) that carries the genes for tumour formation. When the bacterium invades the host cells the Ti plasmid enters the host nuclei. Part of the Ti plasmid become inserted into the chromosome, introducing genes for their growth of the bacterium.
For using Ti plasmid as a vector, researchers have eliminated its tumor causing properties while keeping its ability to transfer DNA into plant cells. This bacterium is called natural genetic engineer because genes carried by Ti plasmid produce effect in several parts of the plant.
18. Differences between intraspecific and inter-specific competition are as follows: Intraspecific competition
15. (i) Recombination
Interspecific competition
(i)
It is competition among The competition is amongst individuals of the same the members of different species. species.
(ii)
The competition is for The competition is for one or all the requirements. a few requirements.
(iii) The competing The competing individuals individuals have similar have different types of adaptations. type of adaptation.
(ii) Plasmid (iii) Primer (iv) Microinjection.
(iv) It is more severe due It is less severe as the similar to similar needs and needs are a few and the adaptations are different. adaptations.
16. Restriction enzyme Eco RI cuts both DNA strands at the same site i.e., between bases G and A in GAATC sequence present in the DNA.
OR
Ecological succession is of two types – primary and secondary succession. Primary succession is a biotic succession which occurs on a previously bare or unoccupied area, e.g., new exposed rock area, sand dunes, igneous rocks, deltas, newly created pond or reservoir. The establishment of a new biotic community is generally slow. Before a biotic community of diverse organisms can become established, there must be soil. Depending mostly on the climate, it takes natural processes several hundred to several thousand years to produce fertile soil on bare rock.
Secondary succession is a biotic succession that occurs in an area from which a community has been removed and
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where nutrients and conditions for existence are present, e.g., cut over forest, abandoned crop land, ploughed fields and lands that have been flooded. Since some soil or sediment is present, secondary succession is faster than primary succession.
in the male and female gonads. Gametogenesis is of two types: spermatogenesis (formation of sperms) and oogenesis (formation of ova).
19. Disruptive natural selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into the distinct groups. This evolutionary process is to be one of the main driving forces behind sympatric speciation. For example, in a forest, a moth population have homozygotes for black or white and heterozygotes are grey. The disruptive selection would favor black and white favor moths over grey moths. This might be because in the forest trees have either light bark or really dark bark. In such environment, it would be less advantageous to have the medium grey colour than the two extreme colours because grey would stand out on either type of tree and predators would have an easy target,
Sympatric speciation occurs when a single population begins to diverge into two without any sort of geographical barrier to separate them. Using the previous example of moths, the black moths would tend to mate with black ones and white moths would mate with white ones because they would produce offsprings that are better adapted to the environment. Eventually, the black and white moths would, split into two reproductively isolated species. In this manner, disruptive natural selection can be the driving force behind sympatric speciation.
20. Gametogenesis is the process by which male and female sex cells or gametes i.e. sperms and ova are formed respectively
Differences between spermatogenesis and oogenesis are given in the following table : Spermatogenesis
Oogenesis
(i)
It is generally completed in the testes and thus mature sperms are released from the testes.
It is often completed in the female reproductive tract or in many animals in water because oocytes are released from the ovaries.
(ii)
A primary spermatocyte divides to form two secondary spermatocytes.
A primary oocyte divides to form one secondary oocyte and one polar body.
A secondary oocyte divides (iii) A secondary spermatocyte divides to to form one ootid and one form two spermatids. polar body. (iv) A spermatogonium forms four spermatozoa.
An oogonium forms only one ovum.
21. (i) Endosperm is persistent in wheat, rice, barely and palm. (ii) As the endosperm develops, it fills up the nucellus. In many seeds no endosperm is seen at maturity although it is always formed at the initial stage of embryo development. During the process of the development of the embryo, the food stored up in the endosperm is continuously drawn up by the developing embryo and thus completely exhausted. Such seeds are known as exalbuminous or non-endospermic. In other cases, where the endosperm grows vigorously and is not completely exhausted by the developing embryo, the seed is known as albuminous or endospermic. The common examples are : exalbuminous – gram, pea, bean, tamarind, orchid, sunflower, etc.; albuminous – castor, poppy, rice, wheat, barley, coconut, palm, grasses etc. 22. Hardy-Weinberg principle states that in a large, randomly interbreeding population, the allelic frequencies in a population remain stable and is constant from generation to generation. This is called genetic equilibrium where gene pool is constant and sum total of all the frequencies is 1.
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Hardy-Weinberg represented this using an algebraic equations which as following:
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p2 + 2pq+ q2 = 1
also, p + q = 1
where, p is frequency of dominant allele and q is frequency of recessive allele. Hence, p2 is the frequency of individuals in the population that are homozygotic dominant i.e., AA and q2 is the frequency of individuals in the population that are homozygotic recessive i.e., aa. 2pq represents frequency of individuals in the population that are heterozygotic or carriers.
24.
Disease
Now, we are given data about individuals showing albinism. Albinism is due to autosomal recessive disorder.
Therefore, number of individuals with albinism is:
q2 = 1/10000 or 0.0001
\ q = 0.0001 = 0.01
Now, p + q = 1
\
So, the frequency of carriers of albinism in the population i.e., 2pq, is
2 pq = 2 × 0.99 × 0.01
p = 0.99
= 0.0198 0.02
2pq =
2 or 1 / 50 100
Thus, in the given population, 1 person in every 50 individuals would be carrier of albinism.
23. (i) The i gene is regulatory gene of lac operon. The i gene codes for the repressor of the lac operon. Since i gene is constitutively expressed, i.e., repressor protein encoded is always available to bind with operator region of the operon and to prevent RNA polymerase from transcribing. Thus, in the presence of an inducer, such as lactose or allolactose, the repressor is inactivated by their interaction. The ‘X’ in the given figure is, thus, inducer. Regulation of lac operon is thereby, positive regulation. (ii) Nonsense mutation is a point mutation in which replacement of a single base nucleotide with another nucleotide converts an amino acid codon into a termination codon. This can truncate the encoded protein and make it nonfunctional. The z gene codes for beta-galactosidase, which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose. As a consequence, E.coli would not be able to catalyse the hydrolysis of a lactose and thus bacteria would not be able to use it as a source of energy, leading to perishment of the bacteria.
Pathogen
Vector
Symptoms
Amoebiasis Entamoeba Contami- Abdominal pain, histolytica nated food diarrhoea, blood in faeces. Malaria
Plasmodium
Anopheles Fever, acute chillness, sweating, nausea
African sleeping sickness
Trypanosoma Glossina palpalis
Kalaazar or Dumdum fever
Leishmania donovani
Phlebotomus
Recurrent fever, anaemia, patient falls asleep. High fever, spleen enlargement, anaemia, darkening of skin.
OR (i) The property to generate a whole plant from any cell/explant is called totipotency. (ii) In case of asexually reproducing crops like banana, virus infections spread rapidly. This is because the vegetative propagules from virus-infected plants contain virus particles. But the shoot apical meristems and some young tissues surrounding them are often free from viruses. Meristem culture, therefore, is often useful in recovering virus-free plants from virus-infected plants or clones. The explants commonly used in meristem culture are shoot tips and nodal segments. These explants are cultured on a medium containing a cytokinin (generally BAP). The plantlets thus obtained are subjected to hardening and, ultimately, established in the field. 25. E.coli cloning vector pBR322 have two antibiotic resistance genes for ampicillin and tetracycline. The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes. For example, you can ligate a foreign DNA at the Bam H I site of tetracycline resistance gene in the vector pBR322. The recombinant plasmids will lose tetracycline resistance due to insertion of foreign DNA. So, when a recombinant DNA bearing gene for resistance to an antibiotic (e.g., ampicillin) is transferred into E.coli cells, the host cells become transformed into ampicillinresistant cells. If we spread the transformed cells on agar plates containing ampicillin, only transformants will grow, untransformed recipient cells will die. Since, due to ampicillin
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resistance gene, one is able to select a transformed cell in the presence of ampicillin. The ampicillin resistance gene in this case is called a selectable marker. Similarly, recombinants can be selected out from nonrecombinants, as the recombinants will grow in ampicillin containing medium but not on that containing tetracycline, but, non-recombinants will grow on the medium containing both the antibiotics. In this manner, one antibiotic resistance gene helps in selecting the transformants, whereas the other antibiotic resistance gene gets ‘inactivated due to insertion’ of alien DNA, and helps in selection of recombinants. 26. (i) Algal bloom. (ii) The excess growth of planktonic algae causes algal bloom. This imparts a distinct colouration to the water bodies. It causes deterioration of the water quality and fish mortality. It may also support excessive growth of floating plants. Water hyacinth (Eichhornia crassipes) is one such plant that may choke lake. Algal bloom and floating plants together would cut off light from submerged plants. The latter would die. There would be a drastic decrease in oxygen replenishment inside water. It may cause organic loading of water. Some bloom forming algae are extremely toxic to human beings and animals. 27. Species area relationship of biodiversity was given by Alexander von Humboldt while he was exploring the South American jungles. He observed that within a region species richness increased with increasing explored area, but only up to a limit. The relation between species richness and area for a wide variety of taxa turns out be a rectangular hyperbola.
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On a logarithmic scale, the relationship is a straight line described by the equation log S = log C + Z log A where S = Species richness A = Area Z = Slope of the line (regression coefficient) C = Y-intercept The value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group or the region. But, if the species MT BIOLOGY
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area relationships among very large areas like the entire continents is analyzed, the slope of the line is much steeper (Z values in the range of 0.6 to 1.2). 28. (i) This is a test cross. (ii)
(iii) Principle of independent assortment is illustrated through the result of this cross. OR Joshua Lederberg and Esher Lederberg demonstrated the genetic basis of adaptation in bacteria with the help of an experiment called Lederberg’s replica plating experiment. They inoculated a dilute suspension of bacteria cells on a semisolid agar plate. The agar plate bearing colonies was used as a ‘master plate’ to obtain its replicas. The replica proliferated but when they attempted to make replicas using plates containing an antibiotic penicillin, most of the colonies failed to grow except a few which were resistant to penicillin. This shows that in the master plate were present a few colonies which were antibiotic resistant before the application of the penicillin. This resistance would have developed in them by chance mutation. This shows that adaptation has genetic basis. The experiment support Darwinism and its view on natural selection. It clearly illustrates that a change in the environment, in this case the introduction of penicillin, gave selective advantage to the penicillin resistant bacteria over the penicillin sensitive bacteria. The penicillin resistant bacteria though already present had no advantage and so were not evident. 29. Greenhouse effect is the progressive, gradual warming of the earth’s atmosphere caused by the insulating effect of carbon dioxide and other green-house gases that have proportionately increased in the atmosphere. The greenhouse effect disturbs the way the Earth’s climate maintains the balance between incoming and outgoing energy by allowing short-wave radiation from the sun to penetrate through to warm the Earth, but preventing the resulting long-wave infrared radiation from escaping back into the atmosphere. There is concern that increasing concentration of greenhouse gases, including carbon dioxide, methane, and man made chlorofluorocarbons, may enhance the greenhouse effect and cause global warming.
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Effects of global warming are : –– Warming of atmosphere will significantly increase its moisture carrying capacity. While the trophosphere warms up, the stratosphere will cool down. This would cause extensive changes in precipitation patterns due to changed pattern of air-mass movements. Besides, the frequency of droughts, floods, etc., is estimated to increase substantially. The climate change will increase threats to human health, predominantly in tropical and subtropical countries, due to change in ranges of disease vectors, water-borne pathogens, etc. –– The global warming may contribute to sea level rise due to the thermal expansion of oceans as it warms, and melting of glaciers and Greenland ice sheets. A rise of even half a meter in sea level would profoundly affect human population, one-third of which lives within 60 km of a coastline. Numerous low-lying islands may be submerged. Inundation of coastal salt marshes and estuaries may deprive of many important birds and fishes, their breeding grounds, forcing their extinction. Strategies to deal with global warming : –– Complete replacement of chlorofluorocarbon with substitutes that have little effect on ozone and global warming. –– Increasing vegetation cover of forests for photosynthetic utilization of CO2. –– Reduction in use of nitrogen fertilizers and instead relying more on nitrogen fixation. –– Limiting use of fossil fuels by developing alternate sources of energy, eg., solar energy, wind energy. –– Increasing use of alternative, renewable, nonpolluting sources of energy like solar energy, wind energy, hydropower etc. –– Preponing the use of hydrogen fuel. OR (i) Photochemical smog is composed of secondary air pollutants. It is formed by interaction of hydrocarbons with nitrogen oxides. The products are ozone, peroxyacyl nitrate (PAN), aldehydes and phenols. Photochemical smog leads to necrosis and chlorosis in plants. (ii) The consequences of deforestation are as follows : –– Change in climate : Deforestation results in reduced rainfall, increased drought, hotter summers and colder winters. –– Soil erosion : Soil is exposed to insolation, dries up and gets eroded by wind and water. It is estimated that 6000 million tonnes of top soil is lost annually in India due to water erosion in the absence of forest cover.
–– Drought : There is very little water in rivers during day season causing drought. –– Loss of biodiversity and germplasm. –– Global warming : Deforestation increases atmospheric CO2 content by releasing carbon stored in organic matter and reduced primary productivity.
30. (i) Yes. Nowadays, the ‘conventional’ farming practices often use chemical methods such as use of insecticides, pesticides, etc. to control plant diseases and pests and to increase yield. However, these chemicals are toxic and extremely harmful, to human beings and animals alike, and have been polluting our environment (soil, ground water), fruits, vegetables and crop plants. Our soil is also polluted through our use of weedicides to remove weeds. These conventional farming practices of using chemical methods, result in killing both useful and harmful life forms indiscriminately. Therefore, it is essential to develop an understanding towards a holistic approach of farming which considers the webs of interaction between myriad of organisms of the field because the eradication of the creatures that are often described as pests is not only possible, but also undesirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive. the holistic approach would not only help in regaining back the fertility of the farmer’s field but also would keep pests, etc., under manageable levels without the use of chemicals. (ii) I would suggest him to switch to organic farming. Due to the overuse of chemical fertilisers, the field has lost natural nutrients as well as beneficial interaction between flora and fauna (insects). Organic farming is the farming practise which does not use artificial fertilisers and pesticides instead it uses biopesticides and biofertilisers. Biofertilisers are micro-organisms which bring about nutrient enrichment of soil by enhancing the availability of nutrients like nitrogen and phosphorus to crops. The main biofertilisers are bacteria, mycorrhizal fungi and cyanobacteria. Bacteria and cyanobacteria have the property of nitrogen fixation while mycorrhizal fungi preferentially absorb phosphorus from soil and passes it to the plant with which they are associated. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.
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In each of the following questions, a statement of Assertion (A) is given and a corresponding statement of Reason (R) is given just below it. Of the statements, mark the correct answer as : (a) if both A and R are true and R is the correct explanation of A (b) if both A and R are true but R is not the correct explanation of A (c) if A is true but R is false (d) if both A and R are false. Plant Respiration 1. Assertion (A) : In respiration, energy of oxidationreduction is utilized for the phosphorylation reaction (i.e., ATP synthesis) and thus the process is called oxidative phosphorylation.
Reason (R) : In photosynthesis, light energy is utilized for ATP synthesis, and thus the process is called photophosphorylation.
2. Assertion (A) : Glycolysis occurs in mitochondrial matrix.
Reason (R) : Krebs’ cycle occurs on the cristae of mitochondria.
3. Assertion (A) : Electron Transport Chain (ETC) is a set of seven electron carriers present in a specific sequence along inner mitochondrial membrane.
Reason (R) : H2O acts as the final hydrogen acceptor during ETS.
4. Assertion (A) : Clostridium tetani is an obligate anaerobe.
Reason (R) : Pyruvic acid is first decarboxylated to acetaldehyde which in turn is converted into ethanol.
7. Assertion (A) : When fats are used as respiratory substrates, value of RQ is less than one.
Reason (R) : During oxidation of fatty acids, O2 absorption is more and CO2 liberation is less.
8. Assertion (A) : Glycolysis occurs in cytoplasm and produces 2ATP and 2NADH2.
Reason (R) : Glycolysis occurs both in aerobic as well as anaerobic respiration.
9. Assertion (A) : Respiratory pathway is considered as an amphibolic pathway.
Reason (R) : Respiratory pathway is involved in both anabolic and catabolic processes.
5. Assertion (A) : The process of fermentation accounts for only a partial breakdown of glucose.
10. Assertion (A) : During aerobic respiration, pyruvic acid formed as a result of glycolysis, undergoes phosphorylation reaction to form acetyl CoA.
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Reason (R) : It cannot live in high O2 concentration.
6. Assertion (A) : End products of alcoholic fermentation are ethanol and CO2.
Reason (R) : In aerobic respiration, complete breakdown of glucose to CO2 and H2O takes place.
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Reason (R) : Phosphorylation reaction is catalyzed by enzyme dehydrogenase.
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WorldMags.net ANSWERS 1. (b) Explanation of ‘A’ & ‘R’ :– The process of synthesis of ATP from ADP and Pi is called as phosphorylation. During respiration, energy of oxidation–reduction is utilized for the phosphorylation reaction and thus the process is called oxidative phosphorylation. It occurs in the inner mitochondrial membrane. During photosynthesis, light energy is utilized for the phosphorylation reaction and thus the process is referred to as photophosphorylation. It takes place in thylakoid membranes. Result : Hence, it is proved that both ‘A’ and ‘R’ are true but as ‘R’ is not the correct explanation of ‘A’, so the answer is option (b). 2. (d) Explanation of ‘A’ & ‘R’ :– Glycolysis is the stepwise oxidation of glucose to pyruvic acid without the use of oxygen. It occurs in the cytoplasm of cells, not in the mitochondria. Krebs’ cycle, also known as TCA cycle (Tricarboxylic acid cycle) or citric acid cycle, takes place in the matrix of mitochondria. It occurs during aerobic respiration only. Result : Hence, it is proved that both ‘A’ and ‘R’ are false, so the answer is option (d). 3. (c) Explanation of ‘A’ & ‘R’ :– The various components of electron transport system include-cytochrome b, 2 types of cytochrome c, ubiquinone, flavoprotein (FMN or FAD), iron-sulphur protein (Fe–S) and enzyme cytochrome oxidase which is intimately associated with cytochrome a and a 3. These components are arranged in four kinds of complexes – Complex I (NADH dehydrogenase complex), Complex II (Succinate dehydrogenase complex), Complex III (Cytochrome bc 1 complex) and Complex IV (cytochrome c oxidase complex). There is a fifth complex, ATP synthase complex, which is involved in ATP synthesis. These complexes are arranged in a definite sequence in the inner mitochondrial membrane. Final step of ETS is called as terminal oxidation, catalyzed by enzyme cytochrome oxidase, during which electrons from cytochrome c are transferred via. cyt a and cyt a 3 (cytochrome oxidase complex) to oxygen. Thus O 2 acts as final e –acceptor (or final hydrogen acceptor) during ETS.
Result : Hence, it is proved that ‘A’ is true and ‘R’ is false, so the answer is option (c). 4. (a) Explanation of ‘A’ & ‘R’ :– The bacteria belonging to the category of obligate anaerobes, respire only anaerobically. They generally get killed under aerobic conditions e.g., Clostridium tetani, C. botulinum. Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a). 5. (b) Explanation of ‘A’ & ‘R’ :– Anaerobic respiration, also called fermentation, involves the partial breakdown of glucose in the absence of oxygen. The end products of fermentation may be ethanol and CO2 (alcoholic fermentation) or lactic acid (lactic acid fermentation). It is a low energy yielding process and one of the end products is always organic. Aerobic respiration is the complete oxidation of glucose into CO2 and H2O in the presence of oxygen. C6H12O6 + 6O2 → 6CO2 + 6H2O + 686 Kcal. It is a high energy yielding process and occurs in most of the higher plants and animals. Result : Hence, it is proved that both ‘A’ and ‘R’ are true but as ‘R’ is not the correct explanation of ‘A’, so the answer is option (b). 6. (a) Explanation of ‘A’ & ‘R’ :– Alcoholic fermentation involves two steps: (i) Decarboxylation of pyruvic acid to acetaldehyde in the presence of enzyme pyruvate decarboxylase, co-enzyme thiamine pyrophosphate (TPP) and Zn2+ as cofactor. (ii) Acetaldehyde accepts 2H atoms from NADH2, in the presence of enzyme ethanol dehydrogenase and changes into ethanol.
Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a).
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7. (a) Explanation of ‘A’ & ‘R’ :– Consider an equation of oxidation of a fatty acid, tripalmitin.
Thus, when fats are used as respiratory substrates, value of RQ comes out to be less than 1 because O2 absorption is more and CO2 liberation is less during the oxidation process. Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a).
8. (b) Explanation of ‘A’ & ‘R’ :– Glycolysis is also called as EMP pathway as its details were given by Embden, Meyerhof and Parnas, in 1930. Glycolysis is the stepwise oxidation of one molecule of glucose into two molecules of pyruvic acid. It occurs in cytoplasm. Glycolysis is called the common pathway as it occurs in both aerobic as well as anaerobic respiration. End products of glycolysis are 2 pyruvic acid molecules, 2ATP and 2NADH2. Result : Hence, it is proved that both ‘A’ and ‘R’ are true but as ‘R’ is not the correct explanation of ‘A’, so the answer is option (b). 9. (a) Explanation of ‘A’ & ‘R’ :– The organic substances (i.e, carbohydrates, fats, proteins, etc) are broken down to release energy by the process of cellular respiration. This process
is considered as a catabolism or a catabolic pathway. However, the breakdown of respiratory substrates provides carbon skeleton for the synthesis of a large number of other essential plant products, such as polysaccharides, proteins, fats, nucleic acids, pigments, cytochromes, etc. Fatty acids is broken down to acetyl CoA before entering the respiratory pathway when it is used as a substrate. But when the organism needs to synthesise fatty acids, acetyl CoA is withdrawn from the respiratory pathway for it. Hence, the respiratory pathway comes into the picture both during breakdown and synthesis of fatty acids. The respiratory pathway, therefore acts both as catabolic as well as anabolic pathway. Thus, it is better to call it amphibolic pathway rather than as a catabolic pathway alone. Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a).
10. (d) Explanation of ‘A’ & ‘R’ :– During aerobic respiration, the final product of glycolysis i.e., pyruvic acid is transported from the cytoplasm into mitochondria which undergoes oxidative decarboxylation. The reaction is catalyzed by an enzyme pyruvate dehydrogenase as follows: Pyruvic acid + CoA + NAD+ Acetyl CoA + CO2 + NADH + H+.
Result : Hence, it is proved that both ‘A’ and ‘R’ are false, so the answer is option (d).
Endocrine System 1. Assertion (A) : Progesterone prepares uterus for pregnancy, implantation and formation of placenta. Reason (R) : Hypersecretion of progesterone causes abortion.
Reason (R) : Calcitriol is the active form of cholecalciferol. It promotes absorption of Ca2+ and phosphorus in the small intestine.
6. Assertion (A) : Excess amount of a parathormone in blood causes softening of bones. Reason (R) : Parathormone mobilizes the release of calcium into the blood from the bones.
4. Assertion (A) : Erythropoietin is a steroid hormone
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Reason (R) : Vasopressin is a peptide hormone, stimulates growth and protein synthesis.
5. Assertion (A) : Melatonin is called “sleep hormone”. Reason (R) : Melatonin produces circadian rhythms .
3. Assertion (A) : Epinephrine is called as emergency hormone. Reason (R) : Stimulation of the sympathetic nerves to adrenal medulla causes release of large quantities of adrenaline and noradrenaline into the blood.
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Calcitriol accelerates bone
2. Assertion (A) : formation.
which increases the production of RBCs.
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7. Assertion (A) : Deficiency of vasopressin causes diabetes insipidus in the patient. Reason (R) : Vasopressin reduces the volume of urine by increasing the reabsorption of water from the urine.
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8. Assertion (A) : Glucagon converts stored glycogen into glucose. Reason (R) : When the blood sugar level decreases, the secretion of insulin is stimulated. 9. Assertion (A) : Failure of secretion of somatotropin
during early age causes dwarfism in the patient. Reason (R) : Somatostatin inhibits the secretion of somatotropin from anterior lobe of pituitary.
10. Assertion (A) : Thymosin is a hormone secreted by thyroid gland. Reason (R) : Thymosin is also called “birth hormone”.
ANSWERS 1. (c) Explanation of ‘A’ & ‘R’ :– Progesterone is a steroid hormone. It is secreted by corpus luteum. It is also secreted by placenta during pregnancy. It stimulates development of the uterine epithelium for pregnancy, implantation and formation of placenta. It also stimulates mammary glands. Progesterone is required to maintain the pregnancy, therefore hyposecretion of progesterone often causes abortion and miscarriage. Result : Hence, it is proved that ‘A’ is true and ‘R’ is false, so the answer is option (c). 2. (a) Explanation of ‘A’ & ‘R’ :– Vitamin D is synthesized in skin epidermis from cholesterol-derived compounds in the presence of sunlight. Vitamin D exists in two forms : calciferol or D2 and cholecalciferol or D3. Cholecalciferol is more important. It circulates in the blood. Calcitriol is active form of D3. It increases absorption of calcium and phosphorus from chyme in the small intestine and accelerates bone formation. Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a). 3. (b) Explanation of ‘A’ & ‘R’ :– Epinephrine is called as emergency hormone. It is secreted at the time of emergency. Stimulation of the sympathetic nerves to adrenal medulla causes large quantities of epinephrine (adrenaline) and norepinephrine (noradrenaline) to be released into the blood circulation. Both the hormones, epinephrine and norepinephrine increases alertness, pupillary dilation, piloerection (raising of hairs), sweating etc. Both hormones increase the heart beat, the strength of heart contraction and the rate of respiration. However, the effect caused by epinephrine has several times as great a metabolic effect as norepinephrine. Therefore, epinephrine is referred to as emergency hormone. Result : Hence, it is proved that both ‘A’ and ‘R’ are true but as ‘R’ is not the correct explanation of ‘A’, so the answer is option (b).
4. (d) Explanation of ‘A’ & ‘R’ :– Erythropoietin is a peptide hormone, secreted by kidney. The oxygen shortage stimulates the kidney cells to secrete the hormone into the blood as a circulating glycoprotein. It stimulates the bone marrow to increase the production of RBCs (erythropoiesis). Whereas, vasopressin is a peptide hormone secreted from posterior lobe of pituitary. It is also called antidiuretic hormone because it increases the reabsorption of water in the distal convoluted tubule and collecting duct of the kidney. Somatotrophic hormone stimulates growth by stimulating protein synthesis. Result : Hence, it is proved that both ‘A’ and ‘R’ are false, so the answer is option (d). 5. (a) Explanation of ‘A’ & ‘R’ :– Melatonin is called “sleep hormone”, because it promotes sleep. Its secretion increases in dim light an decreases in bright light. Melatonin concentration in the blood appears to flow a diurnal (day-night) cycle as it rises in the evening and through the night and drops to a low around noon. Because of this light mediated responses, it is believed to produce circadian rhythms (variation following a 24 hours cycle). Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a). 6. (a) Explanation of ‘A’ & ‘R’ :– Parathormone, also called as Collip’s hormone is released from parathyroid gland. Parathormone (PTH) regulates calcium and phosphate balance between blood and other tissues. In case of hyperparathyroidism excess of parathormrone is secreted. Excess of PTH draws more calcium from the bones. It causes demineralisation, resulting in softening and bending of the bones. Because bones become deformed, they are easily fractured. Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a).
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7. (a)
Explanation of ‘A’ & ‘R’ :– Vasopressin is secreted from posterior lobe of pituitary. Vasopressin is also called as antidiuretic hormone or pitressin. It increases the reabsorption of water in the distal convoluted tubule, collecting tubule and collecting ducts of the nephrons of the kidney. In the absence or deficiency of ADH, the collecting ducts are virtually impermeable to water, and water flows out as urine. Thus, deficiency of vasopressin or antidiuretic hormone (ADH) causes diabetes insipidus i.e., excretion of large volumes of dilute urine.
Result : Hence, it is proved that both ‘A’ and ‘R’ are true and as ‘R’ is the correct explanation of ‘A’, so the answer is option (a). 8. (c) Explanation of ‘A’ & ‘R’ :– Glucagon is secreted by the a cells of the islets of Langerhans. Glucagon acts on the cells of liver and adipose tissue. It stimulates the liver to convert stored glycogen into glucose. Glucagon is also called as anti-insulin hormone. Whereas, insulin is secreted by the b cells of the islets of Langerhans. Insulin is antagonistic to glucagon. Insulin decreases the level of glucose in the blood. It converts glucose into glycogen. When the blood sugar level drops the secretion of insulin is suppressed and when the blood sugar level increases, the secretion of insulin is stimulated. Result : Hence, it is proved that ‘A’ is true and ‘R’ is false, so the answer is option (c).
Ten ‘PoP’ Surgeons in History Surgeons are the rock stars of the medical profession. Here re a few names of the most famous ones in history: John Heysham Gibbon He was known for the invention of the heart-lung machine, and for being the first to perform open heart surgery. Joseph Lister He introduced the idea of sterilizing surgical instruments with carbolic acid as well as using antiseptics to clean wounds. Frederic E Mohs Mohs developed the Mohs Micrographic Surgery (MMS) technique, used to remove skin cancer lesions. Christiaan Barnard This South African surgeon was the first person to perform a heart transplant on a human being. Gavril Ilizarov His speciality was orthopedic surgery and his research into bone 18
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9. (b) Explanation of ‘A’ & ‘R’ :– Somatotropin is secreted by the anterior lobe of the pituitary gland. It stimulates the growth of the body. Dwarfism is caused by the deficiency of growth hormones from childhood. Somatostatin is secreted by the hypothalamus of the brain, delta cells of islets of Langerhans in pancreas and argentaffin cells of the digestive tract. It inhibits the secretion of growth hormone from anterior lobe of the pituitary gland. It also suppresses the release of other hormones from the pancreas and digestive tract. Result : Hence, it is proved that both ‘A’ and ‘R’ are true but as ‘R’ is not the correct explanation of ‘A’, so the answer is option (b). 10. (d) Explanation of ‘A’ & ‘R’ :– Thymosin is a hormone secreted by thymus gland. Thymus gland is located in upper part of the thorax near the heart. Thymus gland is a soft, pinkish, bilobed mass of lymphoid tissues. It is a prominent gland at the time of birth but gradually atrophies in adult. Thymosin stimulates the development of white blood cells which are involved in producing immunity. It also hastens attainment of sexual maturity. Oxytocin is called “birth hormone” as it promotes contraction of uterine muscles during labour and help in parturition. Result : Hence, it is proved that both ‘A’ and ‘R’ are false, so the answer is option (d). nn development led him to invent the procedure used to this day to reshape or lengthen the bones in legs or arms. Norman Bethune This surgeon’s main claim to fame is his development of a mobile blood transfusion process. Lars Laksell If you have been the beneficiary of a radiosurgery treatment, then you have Lars Laksell to thank for it. Paul Randall Harrington The Harrington Rod, designed to help straighten the spine and keep it immobilised, is named after him. It was in use from the 1960s all the way until the late 1990s. John Hunter An outstanding surgeon, he was also known for his compassion, and often waived fees for his poorer patients. Sanjay Gupta He is probably the most well known surgeon alive in the worldpartly thanks to being CNN’s medical correspondent. nn
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1. Which of the following statements regarding universal rules of nomenclature is wrong? (a) The first word in a biological name represents the genus. (b) The first word denoting the genus starts with a capital letter (c) Both the words in a biological name, when handwritten, are separately underlined (d) Biological names are generally in Greek and written in italics. 2. Which of the following is correct? (a) All fungi are filamentous (b) Transfer of DNA from one bacteria to another bacteria cannot take place (c) Virus cannot have both DNA and RNA (d) Protists reproduce asexually only. 3. Select the correct combination of the statements (i-iv) regarding the characteristics of certain organisms. (i) Methanogens are archaebacteria which produce methane in marshy areas (ii) Nostoc is a filamentous blue-green alga which fixes atmospheric nitrogen (iii) Chemosynthetic autotrophic bacteria synthesize cellulose from glucose (iv) Mycoplasma lack a cell wall and can survive without oxygen The correct statements are (a) (ii) and (iii) (b) (i),(ii) and (iii) (c) (ii), (iii) and (iv) (d) (i), (ii) and (iv). 4. Single-celled eukaryotes are included in (a) protista (b) fungi (c) archaea (d) monera. 5. In which of the following classes of fungi, sexual reproduction is absent? (a) Basidiomycetes (b) Deuteromycetes (c) Phycomycetes (d) Ascomycetes.
6.
Algae have cells made up of (a) cellulose, galactans and mannans (b) hemicellulose, pectins and proteins (c) pectins, cellulose and proteins (d) cellulose, hemicellulose and pectins.
7. Which of the following statements is/are incorrect regarding bryophytes? (a) Zygote undergoes meiosis to produce sporophyte (b) Zygote undergoes mitosis to form embryo proper (c) Fertilization takes place in presence of water (d) Sporophyte is parasitic over gametophyte. 8. Pick out wrong statement: (a) Double fertilization is unique to gymnosperms and monocotyledons (b) Sequoia, a gymnosperm, is one of the tallest trees (c) Phaeophyceae members possess chlorophyll a, c, carotenoids and xanthophylls (d) Moss is a gametophyte which consists of two stages namely, protonema stage and leafy stage 9. Aestivation of petals in the flower of cotton is correctly shown in
(a)
(c)
(b)
(d)
10. Find the correct match. (a) Mustard plant : leaves are opposite (b) Mustard plant : leaves are alternate (c) Guava plant : leaves are alternate (d) Guava plant : leaves are whorled
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11. Which one of the following is matched incorrectly? (a) Pinus : coralloid roots (b) Sequoia : tap roots (c) Cycas : unbranched stem (d) Cedrus : branched stem. 12. In cyathium inflorescence (a) single male flower is surrounded by female flowers (b) male and female flowers are borne in different plants (c) there is only one male and one female flowers (d) single female flower surrounded by many peripheral male flowers. 13. Which one of the following is not correct? (a) Early wood is characterized by large number of xylary elements (b) Early wood is characterized by vessels with wider cavities (c) Late wood is characterized by large number of xylary elements (d) Late wood is characterized by vessels with narrower cavities. 14. Apoplastic movement of water in plants occurs through (a) casparian strips (b) plasma membrane (c) intracellular spaces (d) plasmodesmata. 15. Cell A and cell B are adjacent plant cells. In cell A, ys = –20 bars yp = 8 bars. In cell B, ys = –12 bars and yp = 2 bars. Then, (a) water moves from cell A to cell B (b) there is no movement of water between cell A and cell B (c) water moves from cell B to cell A (d) equal amount of water is simultaneously exchanged between cell A and cell B. 16. Select the correct match. (A) Nitrosomonas – Nitrite to nitrate (B) Thiobacillus – Denitrification (C) Nostoc – Free-living nitrogen-fixer (D) Azotobacter – Anaerobic nitrogen-fixer (a) A and B (b) C and D (c) B and C (d) B and D. 17. In C3 cycle for the fixation of every CO2 molecule, the reduction and regeneration steps require (a) 3 ATP and 2 NADPH2 (b) 2 ATP and 2 NADPH2 (c) 2 ATP and 3 NADPH2 (d) 3 ATP and 3 NADPH2. 18. In the electron transport system present in the inner mitochondrial membrane, complexes I and IV are respectively (a) NADH dehydrogenase and FADH2 (b) FADH2 and NADH dehydrogenase (c) NADH dehydrogenase and cytochrome oxidase complex (d) cytochrome bc1 complex and NADH dehydrogenase. 19. FAD acts as an electron acceptor in between 20
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(a) fumaric and malic acid (b) succinic and fumaric acid (c) malic and oxaloacetic acid (d) citric and isocitric acid 20. Which one of the following synthetic growth regulators is used to promote synchronized flowering in pineapple? (a) Benzyl aminopurine (b) Phenylmercuric acetate (c) Indolebutyric acid (d) 2-chloroethylphosphonic acid. 21. Transfer of pollen grains from the anther to the stigma of another flower of the same plant is called (a) xenogamy (b) geitonogamy (c) karyogamy (d) autogamy. 22.
In the diagram given above, parts labelled as ‘A’, ‘B’, ‘C’, ‘D’, ‘E’ and ‘F’ are respectively identified as (a) synergids, polar nuclei, central cell, antipodal cell, filiform apparatus and egg (b) polar nuclei, egg, antipodal cell, central cell, filiform apparatus and synergids (c) egg, synergids, central cell, filiform apparatus, antipodal cell and polar nuclei (d) central cell, polar nuclei, filiform apparatus, antipodal cell, synergids and egg. 23. Consider the following statements and select the correct option. (A) The endomembrane system includes plasma membrane, ER, Golgi complex, lysosomes and vacuoles. (B) ER helps in the transport of substances, synthesis of proteins, lipoproteins and glycogen. (C) Ribosomes are involved in protein synthesis. (D) Mitochondria help in oxidative phosphorylation and generation of ATP. (a) B, C and D are correct (b) A - alone is correct (c) B - alone is correct (d) C - alone is correct. 24. If the length of a double helical DNA is 1.7 meters. The number of base pairs present in the DNA is (a) 5 × 109 (b) 1.7 × 109 9 (c) 3.4 × 10 (d) 1.7 × 105.
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25. Select the incorrect statement. (a) Ribozymes are nucleic acids with catalytic power. (b) Nucleic acids serve as genetic material. (c) Proteins, nucleic acids and polysaccharides are the only three types of macromolecules found in the living system. (d) Collagen is the most abundant protein in the whole of the biosphere and RuBisCo is the most abundant proteins in animal world. 26. Select the correct option with respect to mitosis. (a) Chromatids separate but remain in the centre of the cell in anaphase (b) Chromatids start moving towards opposite poles in telophase (c) Golgi complex and endoplasmic reticulum are still visible at the end of prophase. (d) Chromosomes move to the spindle equator and get aligned along equatorial plate in metaphase. 27. When yellow round heterozygous pea plants are self fertilized, the frequency of occurrence of RrYY genotype among the offsprings is (a) 9/16 (b) 3/16 (c) 2/16 (d) 1/16. 28. Read the following statements and choose the correct option. A. Nitrogenous base is linked to the pentose sugar through a N-glycosidic linkage. B. Phosphate group is linked to 5’-OH of a nucleoside through phosphoester linkage. C. Two nucleosides are linked through 3’ – 5’ N-glycosidic linkage. D. Negatively charged DNA is wrapped around positively charged histone octamer to form nucleosome. E. The chromatin that is more densely packed and stains dark is called euchromatin. (a) A, B and C alone are wrong (b) D alone is wrong (c) C and E alone are wrong (d) A alone is wrong. 29. Beads on string like structures of A are seen in B, which further condense to form chromosomes in C stage of cell division. A B C (a) Chromonema Chromatin Metaphase (b) Chromatin Chromatid Metaphase (c) Chromonema Chromosome Anaphase (d) Chromonema Chromatid Anaphase. 30. Which of the following statements is false regarding predators? (a) Predators keep prey populations under control. (b) Predators help in maintaining species diversity in a community.
(c) If a predator is not efficient, then the prey population would become extinct. (d) Herbivores (predators) have a greater advantage since the plants cannot run away to avoid predation. 31. Given below is an imaginary pyramid of numbers. What could be one of the possibilities about certain organisms at some of the different levels? TC
10
SC
50
PC
500 PP
1
(a) Level PC is “insects” and level SC is “small insectivorous birds”. (b) Level PP is “phytoplanktons” in sea and “whale” on top level TC (c) Level one PP is “pipal trees” and the level SC is “sheep”. (d) Level PC is “rats” and level SC is “cats”. 32. Which of the following relations is correct regarding GPP and NPP of an ecosystem? (a) NPP = GPP – Animal consumption (b) NPP = GPP + Plant respiration (c) NPP = GPP – Plant respiration (d) NPP = GPP + Animal consumption. 33. Select the incorrect statement. (a) Species diversity increases as we move away from the equator towards the poles. (b) Stellar’s sea cow and passenger pigeon got extinct due to over exploitation by man. (c) Lantana and Eichhornia are invasive weed species in India. (d) Among animals, insects are the most species-rich taxonomic group. 34. Match the items of column I with column II and select the correct option. Column I Column II A. Electrostatic 1. Removes gases like SO2 precipitator B. Scrubber 2. Reduces automobile emission C. Catalytic 3. Removes particulate matter converter (a) A – 2, B – 3, C – 1 (b) A – 3, B – 2, C – 1 (c) A – 1, B – 2, C – 3 (d) A – 3, B – 1, C – 2. 35. Which of the following is a correct match between crop, variety and resistance to diseases? Crops Variety Resistance to diseases (a) Wheat Himgiri White rust (b) Brassica Pusa sadabahar Black rot (c) Cowpea Pusa komal bacterial blight (d) Chilli Pusa swarnim Chilly mosaic virus
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36. Match the microbes in column I with their commercial/ industrial products in column II and choose the correct answer. Column I Column II A. Aspergillus niger 1. Ethanol B. Clostridium butylicum 2. Statins C. Saccharomyces cerevisiae 3. Citric acid D. Trichoderma polysporum 4. Butyric acid E. Monascus purpureus 5. Cyclosporin A (a) A – 4, B – 5, C – 2, D – 1, E – 3 (b) A – 3, B – 4, C – 1, D – 5, E – 2 (c) A – 3, B – 4, C – 5, D – 1, E – 2 (d) A – 2, B – 3, C – 4, D – 5, E – 1. 37. Some of the steps involved in the production of humulin are given below. Choose the correct sequence. (i) Synthesis of gene (DNA) for human insulin artificially. (ii) Culturing recombinant E.coli in bioreactors. (iii) Purification of humulin. (iv) Insertion of human insulin gene into plasmid. (v) Introduction of recombinant plasmid into E.coli. (vi) Extraction of recombinant gene product from E.coli. (a) ii, i, iv, iii, v, vi (b) i, iii, v, vi, ii, iv (c) i, iv, v, ii, vi, iii (d) iii, v, ii, i, vi, iv. 38. Match the following and select the correct answer. Column I Column II A. Choanocytes 1. Platyhelminthes B. Cnidoblasts 2. Ctenophora C. Flame cells 3. Porifera D. Nephridia 4. Coelenterata E. Comb plates 5. Annelida (a) A – 2, B – 1, C – 4, D – 5, E – 3 (b) A – 2, B – 4, C – 1, D – 5, E – 3 (c) A – 3, B – 4, C – 1, D – 5, E – 2 (d) A – 3, B – 1, C – 4, D – 5, E – 2. 39. Which among these is not a homoiotherm ? (a) Aptenodytes (b) Testudo (c) Delphinus (d) Ornithorhynchus. 40. Read the following statements and choose the correct option. A. Blood cells secrete fibres of structural proteins called collagen or elastin. B. Neuroglial cells protect and support the nephrons. C. Osteocytes are present in spaces called lacunae. D. Striated muscle fibres are bundled together in a parallel fashion. E. Biceps are involuntary and striated. (a) C and D alone are wrong (b) A and C alone are wrong (c) B and C alone are wrong (d) A, B, and E alone are wrong. 41. Male cockroach differs from female cockroach in having (a) antennae (b) labrum (c) maxillae (d) anal styles. 22
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42. The gastric juice contains (a) trypsin, pepsin, lipase (b) pepsin, lipase, rennin (c) pepsin, amylase, trypsin (d) pepsin, rennin, carboxypeptidase. 43. Pick the correct statement. (a) The contraction of internal intercostal muscles lifts up the ribs and sternum (b) The thoracic cavity is anatomically an air tight chamber (c) Healthy man can inspire approximately 500 ml of air per minute (d) During expiration, the intrapulmonary pressure is slightly below the surrounding atmospheric pressure. 44. If the systolic pressure is 120 mm Hg and diastolic pressure is 80 mm Hg, the pulse pressure is _________. (a) 120 ´ 80 = 9600 mm Hg (b) 120 + 80 = 200 mm Hg 120 = 1.5 mmHg (c) 120 – 80 = 40 mm Hg (d) 80 45. Select the correct statement. (a) The juxta medullary nephrons have reduced Henle’s loop (b) Vasa recta is well developed in cortical nephrons (c) The PCT and DCT are situated in the medulla of the kidney (d) The ascending limb of the Henle’s loop extends as the DCT. 46. The type of joint present between the humerus bone and the pectoral girdle is (a) pivot joint (b) ellipsoid joint (c) gliding joint (d) ball and socket joint 47. Select the answer with correct matching of the structure, its location and function Strucutre Location Function (a) Eustachian Anterior part of Equalizes air pressure tube internal ear on either sides of tympanic membrane (b) Cerebellum Mid brain Controls respiration and gastric secretions (c) Hypotha- Fore brain Controls body lamus temperature, urge for eating and drinking (d) Blind spot Near the place Rods and cones are where optic present but inactive nerve leaves here the eye 48. Select the correct statement regarding the specific disorder of muscular or skeletal system. (a) Muscular dystrophy – age related shortening of muscles (b) Osteoporosis – decrease in bone mass and higher chances of fractures with advancing age
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(c) Myasthenia gravis – Autoimmune disorder which inhibits sliding of myosin filaments (d) Gout – inflammation of joints due to extra deposition of calcium. 49. Identify the origin of sympathetic nerve fibres and the location of their ganglia. (a) They arise from thoraco-lumber region of spinal cord and form ganglia just beside the vertebral column. (b) They arise from thoraco-cervical region of spinal cord and form ganglia just beside the vertebral column. (c) They arise from cranio-sacral region of spinal cord and form ganglia very close to effector organ. (d) They arise from thoraco-lumber region of spinal cord and form ganglia very close to effector organ. 50. The main mineralocorticold in human is (a) aldosterone (b) cortisol (c) testosterone (d) adernaline. 51. Which one of the followng statements about morula in humans is correct? (a) It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA. (b) It has far less cytoplasm as well as less DNA than in an uncleaved zygote. (c) It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote. (d) It has more cytoplasm and more DNA than an uncleaved zygote. 52. The technique called Gamete Intra Fallopian Transfer (GIFT) is recommended for those females (a) who cannot produce an ovum (b) who cannot retain the foetus inside uterus (c) whose cervical canal is too narrow to allow passage for the sperms (d) who cannot provide suitable environment for fertilization. 53. Who proposed that the first form of life could have come from pre-existing non-living organic molecules? (a) S.L. Miller (b) Oparin and Haldane (c) Alfred Wallace (d) Hugo de Vries. 54. Which one among the following is an example for homology? (a) Eye of octopus and mammals (b) Tuber of sweet potato and potato (c) Flippers of penguins and dolphins (d) Thorns and tendrils of Bougainvillea and Cucurbita. 55. Populations are said to be sympatric when _________. (a) two populations live together and freely interbreed to produce sterile offspring (b) two populations are physically isolated by natural barriers (c) two populations are isolated but occasionally come together to interbreed (d) two populations share the same environment but cannot interbreed.
56. Gynaecomastia is a common feature seen in (a) Down’s syndrome (b) Turner’s syndrome (c) Cystic fibrosis (d) Klinefelter’s syndrome. 57. Which one of the following is not a property of cancerous cells whereas the remaining three are? (a) They compete with normal cells for vital nutrients. (b) They do not remain confined in the area of formation. (c) They divide in an uncontrolled manner. (d) They show contact inhibition. 58. Which one of the following life cycle stages of Wuchereria bancrofti is infective to man ? (a) Microfilaria (b) 1st stage larva (c) 2nd stage larva (d) 3rd stage larva. 59. In which one of the following options the two examples are correctly matched with their particular type of immunity? Examples Type of immunity (a) Polymorphonuclear leukocytes Cellular barriers and monocytes (b) Anti-tetanus and anti-snake Active immunity bite injections (c) Saliva in mouth and tears in Physical barriers eyes (d) Mucus coating of epithelium Physiological lining the urinogenital tract barriers. and the HCI in stomach 60. Find out the wrong match. (a) Eosinophils – allergic response (b) Basophils – secrete histamine and serotonin (c) Neutrophils – phagocytic and destroy foreign organisms (d) Monocytes – secrete heparin. 61. Which one is correct regarding electrocardiograph (ECG)? (a) P-wave represents the electrical excitation of the ventricle. (b) QRS complex represents repolarisation of the ventricles. (c) T-wave represents repolarisation of the atria. (d) By counting the number of QRS complexes one can determine the pulse rate. 62. A person suffering from a disease caused by Plasmodium, experiences recurring chill and fever at the time when? (a) The sporozoites released from RBCs are being rapidly killed and broken down inside spleen. (b) The trophozoites reach maximum growth and give out certain toxins. (c) The parasite after its rapid multiplication inside RBCs ruptures them, releasing the stage to enter fresh RBCs. (d) The microgametocytes and megagametocytes are being destroyed by the WBCs.
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63. Which of the following is an opioid drug ? (a) Heroin (b) Cocaine (c) Marijuana (d) Hashish. 64. Shortest phase in the menstrual cycle of women is (a) menstrual phase (b) luteal phase (c) ovulatory phase (d) follicular phase. 65. Which of the following graphs shows the type of natural selection which favours polymorphisms?
(a)
(b)
(c)
(d)
69. Penicillium does not allow the growth of Staphylococcus bacterium and Trichoderma stops the growth of fungus Aspergillus. This type of biotic interaction is/are called (a) parasitism (b) amensalism (c) commensation (d) competition. 70. Human chorionic gonadotropin is secreted by (a) chorion (b) amnion (c) corpus luteum (d) placenta. 71. Refer the given figure showing structure of Malpighian corpuscle. To facilitate ultrafiltration through glomerular capillaries ______.
66. Which of the given below pyramids represents the variation in biomass at different trophic levels in pond ecosystem?
(a)
(c)
(b) (a) Part ‘D’ is narrower than part ‘A’. (b) Part ‘A’ is narrower than part ‘D’. (c) Part ‘C’ is narrower than part ‘D’. (d) Part ‘B’ is narrower than part ‘D’. 72. Select the correct matching of animals, their symmetry, organization and coelom type.
(d)
67. Which species is a decomposer?
(a)
Animal
Symmetry
Organisation
Coelom type
Ctenophores
Radial
Diploblastic
Pseudocoelomates
(a) F (b) G (c) H (d) K. 68. Refer the given figure showing different zones in a deep lake. In which zone of the lake, producers occur throughout from surface to bottom?
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(b) B, C and D (d) E only.
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(b) Echinoderms
Bilateral
Diploblastic Coelomates
(c)
Platyhelmin-
Bilateral
Triploblastic
(d)
Annelids
Biradial
Diploblastic Coelomates
thes
Acoelomates
73. G i v e n b e l o w a r e f o u r s t a t e m e n t s r e g a r d i n g deuteromycetes. (i) It is commonly called imperfect fungi because only the vegetative phases of these fungi are known. (ii) They reproduce only by oospores. (iii) Trichoderma and Colletotrichum belong to this group. (iv) Some members of this group are decomposers while a large number of them are saprophytes. Which two of the above statements are correct? (a) (i) & (iv) (b) (ii) & (iv) (c) (i) & (iii) (d) (ii) & (iii).
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74. Prophase of the first meiotic division is typically longer and complex. It is subdivided into 5 phases: leptotene, zygotene, pachytene, diplotene and diakinesis. Which of the following statements is not correct of these phases? (a) The formation of synaptonemal complex is seen during zygotene stage. (b) The stage of pachytene is characterised by appearance of recombination nodules. (c) Diplotene stage is marked by terminalisation of chiasmata. (d) The compaction of chromosomes continues throughout the leptotene. 75. Match column I with column II and select the correct option from the codes given below. Column I Column II (Elements) (Functions) (A) Calcium (i) Helps in synthesizing cell wall (B) Magnesium (ii) Helps in maintaining turgidity of cells (C) Potassium (iii) Helps in participating in nitrogen metabolism (D) Molybdenum (iv) Helps to maintain chlorophyll structure. A B C D (a) (i) (ii) (iii) (iv) (b) (iv) (iii) (ii) (i) (c) (i) (iii) (ii) (iv) (d) (i) (iv) (ii) (iii). 76. Which of the following shows the correct sequence of flow of electrons in ETS? (a) NADH dehydrogenase → ubiquinone → cytochrome b → cytochrome c1 → cytochrome c → cytochrome a – a3. (b) FADH dehydrogenese → ubiquinone → cytochrome c1 → cytochrome b → cytochrome c → cytochrome a – a3. (c) NADH dehydrogenase → ubiquinone → cytochrome b → cytochrome c → cytochrome c1 → cytochrome a – a3. (d) FADH dehydrogenase → ubiquinone → cytochrome b → cytochrome c → cytochrome c1 → cytochrome a – a3. 77. Examine the figures of different types of chromosomes given below and select the option which represents acrocentric chromosome.
(a)
(b)
(c)
(d)
78. Identify P, Q and R in the graph shown below.
P Q R (a) chlorophyll b chlorophyll a carotenoids (b) chlorophyll a chlorophyll b carotenoids (c) chlorophyll a carotenoids chlorophyll b (d) chlorophyll b carotenoids. chlorophyll a. 79. Given below are four statements (A - D) each with one or two blanks. Select the option which correctly fills up the blanks in two statements. Statements : (A) Thymus secretes (i) which help in differentiation of (ii) . (B) The adrenal medulla secretes (i) which stimulates the breakdown of (ii) to increase the blood glucose concentration during emergency situations. (C) The Leydig’s cells or (i) present in the intertubular spaces in testis, produce a group of hormone called (ii) . (D) Thyroid gland secretes (i) and triiodothyronine. (ii) is essential for the normal rate of hormone synthesis in the thyroid. (a) (A) - (i) melatonin, (ii) T-lymphocytes (B) - (i) adrenaline, (ii) fat (b) (B) - (i) catecholamine, (ii) glycogen (C) - (i) interstitial cells, (ii) testosterone. (c) (B) - (i) catecholamine, (ii) glycogen (D) - (i) thyroxine, (ii) iodine (d) (D) - (i) parathyroid hormone, (ii) calcium (A) - (i) thymosin, (ii) B-lymphocytes. 80. Which of the following statements is incorrect for the reason of opting scientific names over vernacular names? (a) Vernacular names cannot be used in communications amongst scientists. (b) Some vernacular names have incorrect meaning. (c) Some vernacular names are particularly used for specific organisms only. (d) All organisms do not occur in an area.
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81. Which of the following options is correct regarding the average composition of different macromolecules in a living cell ? Lipids Proteins Carbohydrates (a)
5 – 10
20 – 25
5
Nucleic acids 1–2
(b)
2
10 – 15
3
5–7
(c)
10
10 – 15
3
12 – 15
86. Which of the following methods is/are used in recovery of healthy plants from diseased plants? (a) Embryo culture (b) Meristem culture (c) Suspension culture (d) Anther culture. 87. Refer the given figure showing a cell of soyabean. What is the function of ‘A’?
(d) 2 20 – 25 15 5–7 82. Female plant is diploid and male plant is tetraploid. Find out the correct match. Embryo
(a)
3n
Endo-
Egg
sperm
Integument
Pollen
4n
2n
n
2n
Aleurone layer
4n
(b)
2n
6n
2n
4n
4n
2n
(c)
2n
3n
2n
4n
n
3n
(d) 6n 4n 3n n 2n n 83. Refer the given figure showing citric acid cycle. What changes take place during the conversion of A to B?
(a) It protects nitrogenase from oxygen (b) It protects bacterioids from nitrogenase (c) It secretes chemical attractants that cause curling of root hair around nitrogen-fixing bacteria (d) Both (b) and (c). 88. Plants require sulphur for (a) ATP synthesis (b) protein synthesis (c) glucose synthesis (d) DNA replication. 89. Phagocytic cells of liver are (a) Kupffer’s cells (b) acinar cells (c) Deiter cells (d) Hensen’s cells. 90. The most likely reason for the development of resistance against pesticides in insect damaging crops is (a) genetic recombination (b) directed mutations (c) acquired heritable changes (d) random mutations. Answer key
(a) CO2 is liberated (b) NAD+ is converted to NADH + H+ (c) GTP is formed from GDP (d) All of these. 84. 5′ A G C T 3′ is the recognition sequence and cleavage site for which of the following enzyme? (a) Alu I (b) Bam H I (c) Eco R I (d) Hin d III 85. The colour of high yielding Mexican wheats were not liked by the Indians. It was originally red grained. Their cultivation was adopted in India on large scale only when exposure to gamma radiations converted them to amber grained. Which of following methods of plant-breeding has been put into practise in the given case? (a) Polyploid breeding (b) Interspecific hybridisation (c) Tissue culture (d) Mutation breeding. 26
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1. 6. 11. 16. 21. 26. 31. 36. 41. 46. 51. 56. 61. 66. 71. 76. 81. 86.
(d) (a) (a) (c) (b) (d) (a) (b) (d) (d) (a) (d) (d) (c) (a) (a) (b) (b)
2. 7. 12. 17. 22. 27. 32. 37. 42. 47. 52. 57. 62. 67. 72. 77. 82. 87.
(c) (a) (d) (a) (a) (c) (c) (c) (b) (c) (a) (d) (c) (c) (c) (b) (a) (a)
3. 8. 13. 18. 23. 28. 33. 38. 43. 48. 53. 58. 63. 68. 73. 78. 83. 88.
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(d) (a) (c) (c) (a) (c) (a) (c) (b) (b) (b) (d) (a) (c) (c) (d) (d) (b)
4. 9. 14. 19. 24. 29. 34. 39. 44. 49. 54. 59. 64. 69. 74. 79. 84. 89.
(a) (d) (c) (b) (a) (a) (d) (b) (c) (a) (d) (a) (c) (b) (c) (c) (a) (a)
5. 10. 15. 20. 25. 30. 35. 40. 45. 50. 55. 60. 65. 70. 75. 80. 85. 90.
(b) (b) (c) (d) (d) (c) (c) (d) (d) (a) (d) (d) (c) (d) (d) (c) (d) (c) nn
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Ecological succession • Biotic or ecological succession is the natural development of a series of biotic communities at the same site, one after the other till a climax community develops which does not evolve further because it is in perfect harmony with the environment of the area. • A biotic community is influenced by biotic factors, physico-chemical factors and geographical factors. • During succession some species colonise an area and their population become more numerous, whereas population of other species decline and even disappears. • The present day communities in the world have come into existence because of succession that has occurred over millions of years since life started on earth. • Actually succession and evolution would have been parallel processes at that time.
• The first biotic community which develops in a bare area is called pioneer community. • Climax community is the stable, self perpetuating and final biotic community that develops at the end of biotic succession and is in perfect harmony with the physical environment. • Climax community is also termed as climatic climax community. • Climax community has maximum diversity and niche specialization. • The various biotic communities that develop during biotic succession or the intermediate communities between the pioneer and climax communities are termed as seral stages or transitional communities. • The entire sequence of developmental stages of biotic succession from pioneer to a climax community is known as sere.
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General processes of succession • Succession is completed in following steps : • Nudation : Formation of bare area without any form of life is called nudation. The cause of nudation may be climatic (e.g., wind, erosion, floods, drought, storm, frost), topographic (e.g., landslide, volcanic eruptions) or biotic (e.g., epidemic, human activities, fire). • Invasion : Successful establishment of a species in this bare area is called invasion. It is completed in three steps: migration, ecesis or establishment and aggregation. –– The transfer of seeds, spores or other propagules of the first settler species to the bare area is called migration. –– The species which get invaded to the bare area must grow, establish and reproduce for successful succession. This depends largely on the characteristics of substratum, climatic and other environmental factors of the area. Those species which get adjusted to this situation ultimately get established. As a result of ecesis, individuals of the species become established in the area. –– After ecesis, the individuals of the species increase in number by reproduction and they get close to each other. This process is called aggregation. • Competetion and coaction : Initially, many species invade the bare area simultaneously. However, those which find environment favourable ultimately establish and get aggregated at the limited available area. This results in competition mainly for space and nutrition. • Competetion may be interspecific or intraspecific. • Various kinds of interspecific and intraspecific interactions 28
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affect the individuals of species in various ways called coaction. The species which are unable to compete are ultimately discarded. • Reaction : The living organisms reciprocally influence and get influenced by the environment. This is known as reaction. As a result of reaction, changes take place in soil, water, light conditions, temperature etc. of the area. Thus, the environment of the area gets modified, becoming unsuitable for the existing community which in course of time gets replaced by another community (seral community). • Stabilization : Finally, the terminal community becomes stabilized in the prevailing conditions.
Types of ecological succession • Ecological succession is of two types – primary and secondary succession.
Primary succession • Primary succession is a biotic succession which occurs on a previously bare or unoccupied area, e.g., new exposed rock area, sand dunes, igneous rocks, deltas, newly created pond or reservoir. • The establishment of a new biotic community is generally slow. Before a biotic community of diverse organisms can become established, there must be soil. • Depending mostly on the climate, it takes natural processes several hundred to several thousand years to produce fertile soil on bare rock. • The first group of organisms establishing there are known as the pioneers, primary community or primary colonizers. • As a result of ecological succession, changes in vegetation occur, which in turn affect food and shelter for various types of animals. • Based on the nature of the habitat, succession of plants is of two types-hydrarch and xerarch. • Hydrosere or hydrarch starts in regions where water is in plenty and progress from hydric to mesic conditions (adequate moisture conditions). • Xerosere or xerarch starts in regions where moisture is present in minimal amounts such as dry deserts, rocks etc. and it progress from xeric to mesic conditions. • Both hydrarch and xerach successions lead to medium water conditions (mesic)neither to dry (xeric) nor too wet (hydric).
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Some examples of primary succession
Lithosere • Lithosere is a type of xerosere originating on bare rock surfaces. • The various stages and their component plant species of a lithosere appearing on a rock are as follows : • Lichen stage: Lichens are the first to appear on a bare rock. • Lichens are resistant to desiccation and temperature extremes. • Their propagules dropped by wind on a rock moistened by rain or dew, develop attaching rhizoids and grow into lichens (crustose lichens like - Rinodina, Rhizocarpon). • The lichens produce organic acids which corrode the rock surface. • This produces depressions and releases minerals which facilitate further growth of the lichens. • The lichens hold the fine particles of rock along with the sand particles brought by wind in the depressions to initiate soil formation. • Dead lichens contribute organic matter to the forming soil which slowly becomes fertile. • Now larger lichens arrive. These are foliose lichens like Dermatocarpon, Parmelia. They increase soil and its organic matter, and kill the earlier small lichens by shading them. • Moss stage: In the meagre soil formed by lichens moss appears as first plant community. Mosses (for e.g., Tortula, Grimmia) can gain a hold in even a thin layer of lichen remains and rock dust. • Mosses being taller and gregarious, kill the lichens with their shade and replace them. • Mosses break up the rock further and add their own dead bodies to the soil, increasing its thickness, fertility and water-holding capacity. • Herbs stage: This stage is of soil-binding annual grasses (e.g., Aristida, Poa, Eleusine) that hold the rock particles in place. • Their roots penetrate deeper, causing more weathering of rocks. • Being larger, the grasses replace the mosses. • As time passes, grasses die adding more moisture-retaining humus to the soil. • This changes the composition of the soil and gradually develops conditions in which perennial grasses (e.g., Cynodon, Cymbopogon, Heteropogon) can grow. • These grasses rapidly spread by means of runners and rhizomes. • They further enrich the soil, in which hard annual herbs, then biennial and perennial herbs can grow. • All these plants, in turn, add to the thickness and fertility of the soil.
• Shrub stage: Now the soil can support shrubs, which gradually replace the grasses and herbs (e.g., Zizyphus, Caparis, Rhus). • The roots of the shrubs go deeper and fragment more rock material, making the soil still thicker. • Their dead, decaying leaves add organic matter that makes soil more fertile and moist. • Tree stage : Finally, the trees come in and replace the shrubs. They by transpiration, make the environment cool and moist. • The trees are not replaced and form the climax community. • The type of climax community is determined by the climate of the region. • Rain forests develop in the moist, warm, tropical zones and coniferous or deciduous forests grow in the cool temperate regions. • The plants of each community modify the soil by adding humus, enabling the next community to grow. • Each seral community modifies the environmental conditions in such a way that these are less favourable for itself and more favourable for the next community. In fact, each community acts to end itself. • Succession of plant communities is accompanied by succession of animal communities. • Each plant community in the sere is inhabited by a characteristic group of animals. The grass and shrub communities have spiders and grasshoppers. • The forest community has ants, termites, earthworms, snails, centipedes, millipedes, sow bugs, birds, squirrels and many more. • Development of climax forests on bare rocks or sand dunes, i.e., primary succession, takes at least 1,000 years. • In the areas having less rainfall, the primary succession produces grasslands. The shrub and tree stages fail to come in such places.
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Hydrosere • Series of biotic communities that develop in a newly formed pond or lake is called hydrosere. • The various stages together with their chief components of plant species during primary succession in water are : • Phytoplankton stage : This stage constitute the pioneer community. Some blue-green algae, green algae, diatoms and bacteria etc. are the first organisms to colonize the primitive medium of the pond. • Rooted submerged stage : As a result of death and decomposition of phytoplanktons, and their mixing with the silt, there develops a soft mud at the bottom of pond. • This new habitat which tends to be a bit shallower and where light penetration may now occur easily becomes suitable for the growth of rooted submerged hydrophytes. E.g., Hydrilla, Ceratophyllum, Potamogeton etc. • Floating stage : The roots of the plants of this stage are anchored in the floor and their leaves float on the surface of water. E.g., Nymphia, Nelumbium. • Some free floating plants also arrive. E.g., Lemna, Pistia, Azolla, Eichhornia, Salvinia etc. The amount of water decreases very quickly. Soil is quickly built - up. In a short time, water becomes very shallow. • Reed-swamp stage : This stage is also known as amphibious stage as the plants of community are rooted but most parts of their shoots (assimilatory organs) remain exposed to air. E.g., Typha, Polygonum, Ipomea, Marsilia.
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•
•
•
•
•
•
•
They possess well-developed rhizomes and form a very dense vegetation. Marsh or sedge - meadow stage : Because of the successive decrease in water level and further changes in the substratum, species of Carex, Juncus, Cyperus, Eleocharis, etc. colonize this area. With the help of their much branched rhizomatous systems they form a mat-like vegetation towards the centre of the pond. As a result of high rate of transpiration, there is much rapid loss of water, and sooner or later the mud is exposed to air due to which nutrients like ammonia, sulphides, etc. become oxidized to nitrates and sulphates. These mesic conditions approach the area and marshy vegetation disappear gradually providing the way for the next stage. Woodland stage : Due to disappearance of marshy sedge-meadow stage, soil becomes drier for most time of the year. This area is now invaded by terrestrial plants, which are some shrubs and trees. By this time there is much accumulation of humus with rich flora of microorganisms. Thus, mineralization of soil favours the outcome of new trees in the area. Climax forest stage : Forest stage is the climax community. In tropical climates with heavy rainfall, there grows mixed forest of Acer, Quercus, etc. But in regions of moderate rainfall, there develops deciduous forests.
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Secondary succession • This is the succession of communities in previously inhabited areas which have been naturally or artificially disturbed and where soil and some organisms are already present. • Secondary succession is a biotic succession that occurs in an area from which a community has been removed and where nutrients and conditions for existence are present, e.g., cut over forest, abandoned crop land, ploughed fields and lands that have been flooded. • Natural phenomena, such as avalanches (massive snowslides), landslides, volcanic eruptions, earthquake, floods, prolonged severe dought and forest fires set by lightning or human activity, destroy existing communities and pave the way for secondary succession. • An abandoned field, heavily overgrazed pasture, deforested tract also provide a site for secondary succession. • Secondary succession is much faster than the primary succession because the soil and certain organisms are already present. • Surviving seeds, underground stems, persisting and new invading species rapidly grow on the return of favourable conditions. • This re-establishes the biotic community through necessary seral changes in due course of time. • In an abandoned field, grasses and annual weeds quickly move in and cover the soil with a carpet of low vegetation. • Some taller perennial plants move in. These new plants shade the ground and their long roots monopolize the soil water. • The seedlings of the pioneer species now find difficult to grow. The tall herbs are deprived of sunlight and water by the shrubs, which get the same treatment from the trees.
• Finally, a forest of climax species is established to persist till it is disturbed. • A destroyed grassland may take 50 – 100 years and a damaged forest over 200 years to recover fully. • Fugitive species : The species which occur in an area for a short period only during ecological succession are known as fugitive species. Table : Differences between primary succession and secondary succession Primary succession
Secondary succession
1. It occurs in an area which Secondary succession has been bare from the occurs in an area which has beginning. been denuded recently. 2. Soil is absent in the Soil is present in the beginning of primary area where secondary succession. succession begins. 3. There is no humus in the Humus is present from the beginning. very beginning. 4. Reproductive structures of Reproductive structures of any previous community the previous occupants are are absent. present in the area. 5. Pioneer community comes Pioneer community from outside. develops partly from previous occupants and partly from migrants. 6. Seral communities many.
are Seral communities are a few.
7. Primary succession takes a Secondary succession takes long time for completion, less time for completion, 1000 years or more. 50-200 years.
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Importance of biotic succession
• It tells us how a biotic seral stage like grasses and herbs of a pasture can be maintained by not allowing the biotic succession to proceed further through interference like grazing and fire. • Information gained through biotic succession is used in having controlled growth of one or more species by preventing their superiors to invade the area, e.g., maintenance of teak forest. • Dams are protected by preventing siltation and biotic succession to occur. • It gives information about the techniques to be used during reforestation and afforestation. Points to be noted • Autogenic succession : When the succession has begun, the vegetation itself is responsible for replacing itself by changing existing environmental conditions. • Allogenic succession : When in succession other conditions (not vegetation itself) are responsible for replacing communities, then it is called allogenic succession.
• Autotrophic succession is characterised by early and continued dominance of autotrophic organisms like green plants. It starts in a predominantly inorganic environment and the energy flow is maintained indefinitely. • Heterotrophic succession is characterised by early dominance of heterotrophs such as bacteria, fungi and actinomycetes. It begins in a predominantly organic environment and there is a progressive decline in the energy content. • Induced succession occurs due to extensive external interference. Here the initial community has high productivity which gradually decreases. Agriculture can be deemed as an example of induced succession. Here a steady stage is maintained for an ultimate good harvest. • Due to environmental thrust and human interference the climax vegetation may retrograde into shrub land or savannah. This is referred to as retrogressive succession. • When the succession doesn’t proceed through its normal course and side tracks, the advancement line is called deflated succession.
Table : Trends to be expected in the development of ecosystem. Ecosystem Attributes
Developmental Stages
Mature Stages
Community energetics 1.
Gross production/community respiration (P/R ratio)
Greater or less than 1
Approaches 1
2.
Gross production/standing crop biomass (P/B ratio)
High
Low
3.
Biomass supported/unit energy flow (B/E ratio)
Low
High
4.
Net community production (yield)
High
Low
5.
Food chains
Linear, predominantly grazing
Web-like, predominantly detritus
Community structure 6.
Total organic matter
Small
Large
7.
Inorganic nutrients
Extrabiotic
Intrabiotic
8.
Species diversity - variety component
Low
High
9.
Species diversity - equitability component
Low
High
10. Biochemical diversity
Low
High
11. Stratification and spatial heterogeneity (pattern diversity)
Poorly organized
Well-organized
Life history 12. Niche specialization
Broad
Narrow
13. Size of organism
Small
Large
14. Life cycles
Short, simple
Long, complex
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WorldMags.net Nutrient cycling
15. Mineral cycles
Open
Closed
16. Nutrient exchange rate, between organisms and environment
Rapid
Slow
17. Role of detritus in nutrient regeneration
Unimportant
Important
Selection pressure 18. Growth form
For rapid growth (“r-selection”)
For feedback (“K-selection”)
19. Production
Quantity
Quality
control
Overall homeostasis 20. Internal symbiosis
Undeveloped
Developed
21. Nutrient conservation
Poor
Good
22. Stability (resistance to external perturbations)
Poor
Good
23. Entropy
High
Low
24. Information
Low
High
Multiple Choice Questions 1. Ecological succession on sand is (a) psammosere (b) xerosere (c) halosere (d) hydrosere. 2. The primary succession refers to the development of communities on a (a) forest clearing after devastating fire (b) newly-exposed habitat with no record of earlier vegetation (c) freshly cleared crop field (d) pond, freshly filled with water after a dry phase. 3. Most of the plants cultivated in agriculture are actually belonging to the succession level (a) early 1° succession (b) late 1° succession (c) early 2° succession (d) late 2° succession. 4. Succession is (a) orderly process of community change till stability (b) gradual, directional and continuous process (c) series of biotic communities that appear gradually in a barren area (d) all of these. 5. Lichen is the pioneer vegetation on which succession ? (a) Hydrosere (b) Lithosere (c) Psammosere (d) Xerosere.
6. Primary succession on land occurs as (a) lichen → mosses → annual grass → shrubs → trees (b) mosses → lichen → annual grass → shrubs → trees (c) plankton → submerged → floating stage → marsh stage → climax stage (d) all of the above. 7. Last stable community in succession dependent on climate is (a) seral community (b) climax community (c) both (a) and (b) (d) none of these. 8. Which of the following sequence is correct? (a) Nudation → migration → competition → ecesis stabilization (b) Nudation → migration → ecesis → competition reaction (c) Nudation → ecesis → migration → competition reaction (d) Nudation → competition → migration → ecesis reaction.
→ → → →
9. In ecological succession the climax community is best recognised by the following state (a) P = R (b) P > R (c) P < R (d) P ≠ R.
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10. In primary succession on rocks, the pioneer species are usually (a) algae (b) fungi (c) lichens (d) bryophytes.
18. Early colonists of succession are more ______ selected organisms than late colonists. Early plant colonists begin life as ______ seeds, have ______ development, produce ______ “clutches”, and have ______ niches.
11. Both hydrarch and xerarch successions lead to (a) medium water conditions (b) xeric conditions (c) highly dry conditions (d) excessive wet conditions.
12. Succession involves a turnover of species during (a) the seasons of the year (b) ecological time (c) microevolutionary time (d) macroevolutionary time. 13. The kind of climax community in an area depends mostly on the area’s (a) pool of available colonists (b) soil organisms (c) climate (d) bedrock. 14. Primary succession takes much longer than secondary succession, because it involves (a) development of the soil (b) development of a seed bank (c) colonization by organisms that are farther away (d) colonization by more K-selected organisms.
Read the above paragraph and select the correct sequence of words to complete it. (a) K, tiny, slow, small, limited (b) r, tiny, rapid, large, large (c) r, tiny, rapid, small, limited (d) K, tiny, slow, large, large.
19. During a succession, the number of species ______, the community biomass ______, and the community’s ratio of respiration to photosynthesis ______. At climax, the rate of photosynthesis is ______ the rate of respiration.
Read the above paragraph and select the correct sequence of words to complete it. (a) increases, increases, increases, equal to (b) increases, decreases, increases, lesser to (c) decreases, decreases, decreases, equal to (d) increases, increases, decreases, equal to.
20. Early plant colonists are ______ likely to have secondary compounds, ______ likely to tolerate shade, and ______ likely to be out competed than climax plant species.
15. Early colonists in a primary succession are usually lichens, legumes, and plants with mycorrhizae, which suggests that colonization is easier when an organism has a (a) competitive edge (b) parasitic association (c) commensual association (d) mutualistic association.
16. Most agriculture makes use of plants from (a) early primary succession (b) early secondary succession (c) late primary succession (d) late secondary succession.
1. 6. 11. 16.
Read the above paragraph and select the correct sequence of words to complete it. (a) more, more, less (b) less, less, less (c) less, more, less (d) less, less, more.
Answer Key (a) (a) (a) (b)
2. 7. 12. 17.
(b) (b) (b) (b)
3. 8. 13. 18.
17. The two forms of succession are ______ succession, in which a community develops where no community existed before, and _______ succession, in which a community develops again after a disturbance. The conversion of a lake to a terrestrial community is a special form of ________ succession. Read the above paragraph and select the correct sequence of words to complete it. (a) primary, secondary, tertiary (b) primary, secondary, primary (c) secondary, primary, secondary (d) primary, secondary, secondary. 34
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(d) (b) (c) (b)
4. 9. 14. 19.
(d) (a) (a) (a)
5. 10. 15. 20.
(b) (c) (d) (d)
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Increased blood cholesterol may lead to its deposition in the internal wall of the blood vessels like arteries and veins which causes high blood pressure and heart problems.
Blood corpuscles Blood corpuscles or formed elements are of three types: erythrocytes, leucocytes and thrombocytes.
Erythrocytes
The content for PMT Biology is very vast. It does not allow students to engage in enquiry so as to develop meaningful knowledge. Essential topic for PMT is presented here to enable students grasp the topic, analyse the kind of questions appearing in PMTs, practice and score HIGH.
Blood and Hemostasis Blood Blood is a mobile fluid connective tissue composed of a fluid, the plasma and the cells, the blood corpuscles. Blood forms about 30 - 35 percent of the extracellular fluid (ECF). The volume of blood in an adult person of 70 kg weight is about 5.5 litres. It is a slightly alkaline fluid having pH 7.4 pH of blood in arteries is more than in veins.
Plasma Plasma is slightly alkaline non-living intercellular substance which constitutes about 60 % part of the blood. It is a pale yellow but transparent and clear fluid. It is composed of water and mineral salts. All salts constitute about 0.9 % of plasma. Buffer of the blood is sodium bicarbonate. Nutrients include glucose, fatty acids, phospholipids, cholesterol, fats, amino acids, nucleosides, etc. Plasma proteins constitute about 7 to 8 % part of plasma. These mainly include albumin, globulin, immunoglobulin, prothrombin and fibrinogen, immunoglobulins and other defence compounds, excretory substances including ammonia, urea, uric acid. The albumins are the most abundant of the plasma proteins and are synthesized by the liver. Serum is plasma with fibrinogen and other proteins involved in clotting removed as a result of clotting. Dissolved gases include oxygen, carbon dioxide and nitrogen. Other substances present are anticoagulant, hormones, vitamins and enzymes. Blood glucose level is about 80–100 mg per 100 mL of blood 12 hours after a normal meal. But its concentration rises more soon after a carbohydrate rich diet. The normal amount of blood cholesterol is 80–180 mg in 100 mL of blood plasma.
Erythrocytes or red blood corpuscles (RBCs) are the most abundant cells in the human body. The total number of RBCs per microlitre of blood is termed as the total count of RBCs. A normal adult man and woman have 5 and 4.5 million RBCs per cubic millimeter of blood respectively. An abnormal rise in RBC count is called polycythemia. Decrease in the number of RBC is called erythrocytopenia which causes oxygen shortage in the blood and tissues. The shape of RBCs vary in different classes of vertebrates. Red blood corpuscles of all adult mammals are enucleated (nonnucleated). They are mostly biconcave and circular, however camel and Llama RBCs are oval. The RBCs impart red colour to the blood. Red colour is due to the presence of haemoglobin. Matured mammalian RBCs do not have cell organelles including nucleus, mitochondria, ribosomes, centrioles and endoplasmic reticulum. Thus, almost entire cytoplasm is filled with haemoglobin. Haemoglobin is a conjugate protein which is made up of a protein called globin and a non protein group heme (= haeme), hence the name haemoglobin. Heme is an iron ++ (Fe ) – porphyrin complex. A mammalian haemoglobin molecule is a complex of 4 heme molecules joined with 4 globin molecules. 100 ml of blood of a normal man contains 15 g of haemoglobin and of normal woman an average of 13 g of haemoglobin. Less amount of haemoglobin leads to anaemia. The life of an RBC is about 120 days. The worn out RBCs are destroyed in the spleen and liver. Their pigment is degraded to yellowish pigment bilirubin which is excreted in bile. Concave surface of mammalian RBCs helps in increasing the surface area. The adult haemoglobin molecule is made of 2 alpha chains with 141 amino acids each and 2 beta chains with 146 amino acids each. People living in hills have more RBCs.
Erythrocyte production The site of erythrocyte production is the soft interior of certain bones called bone marrow, specially, the red bone marrow.
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With differentiation, the erythrocyte precursors produce hemoglobin, but then they ultimately lose their nuclei and organelles — their machinery for protein synthesis. Young erythrocytes in the bone marrow still contain a few ribosomes, which produce a web-like (reticular) appearance when treated with special stains, an appearance that gives these young erythrocytes the name reticulocytes. Normally, erythrocytes lose st these ribosomes that 1 day after leaving the bone marrow, so reticulocytes constitute only about 1 per cent of circulating erythrocytes. In the presence of unusually rapid erythrocyte production, however, many more reticulocytes can be found in the blood, a phenomenon of clinically diagnostic usefulness. Because erythrocytes lack nuclei and most organelles, they can neither reproduce themselves nor maintain their normal structure for very long. The average life span of an erythrocyte is approximately 120 days, which means that almost 1 per cent of the erythrocytes are destroyed and must be replaced every day. This amounts to 250 billion cells per day! The production of erythrocytes requires the usual nutrients needed to synthesize any cell: amino acids, lipids and carbohydrates. In addition, both iron and certain growth factors, including the vitamins folic acid and B12, are essential. Iron is the element to which oxygen binds on a hemoglobin molecule within an erythrocyte. Small amounts of iron are lost from the body via the urine, feces, sweat, and cells sloughed from the skin. Women lose an additional amount via menstrual blood. In order to remain in iron balance, the amount of iron lost from the body must be replaced by ingestion of ironcontaining foods. Particularly rich sources of iron are meat, liver, shellfish, egg yolk, beans, nuts, and cereals. A significant upset of iron balance can result in either iron deficiency, leading to inadequate hemoglobin production,
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or an excess of iron in the body, with serious toxic effects (hemochromatosis). The body has a considerable store of iron, mainly in the liver, bound up in a protein called ferritin. Ferritin serves as a buffer against iron deficiency. As old erythrocytes are destroyed in the spleen (and liver), their iron is released into the plasma and bound to an iron-transport plasma protein called transferrin. Transferrin delivers almost all of this iron to the bone marrow to be incorporated into new erythrocytes. Recirculation of erythrocyte iron is very important because it involves 20 times more iron per day than the body absorbs and excretes. Folic acid, a vitamin found in large amounts in leafy plants, yeast, and liver, is required for synthesis of the nucleotide base thymine. It is, therefore, essential for the formation of DNA and thus for normal cell division. When folic acid is not present in adequate amounts, impairment of cell division occurs throughout the body but is most striking in rapidly proliferating cells, including erythrocyte precursors. As a result, fewer erythrocytes are produced when folic acid is deficient. The production of normal erythrocyte numbers also requires extremely small quantities (one-million of a gram per day) of a cobalt-containing molecule, vitamin B12 (also called cobalamine), because this vitamin is required for the action of folic acid. Vitamin B12 is found only in animal products, and strictly vegetarian diets tend to be deficient in it. Also, the absorption of vitamin B12 from the gastrointestinal tract requires a protein called intrinsic factor, which is secreted by the stomach. Lack of this protein, therefore, causes vitamin B12 deficiency, and the resulting erythrocyte deficiency is known as pernicious anemia.
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As we know, iron, folic acid, and vitamin B12 must be present for normal erythrocyte production, or erythropoiesis. However, none of these substances constitutes the signal that regulates the production rate. The direct control of erythropoiesis is exerted primarily by a hormone called erythropoietin, which is secreted into the blood mainly by a particular group of hormone-secreting connective tissue cells in the kidneys (the liver also secretes this hormone but to a much lesser extent). Erythropoetin acts on the bone marrow to stimulate the proliferation of erythrocyte progenitor cells and their differentiation into mature erythrocytes. The erythropoietin secretion rate is increased markedly above basal values when there is a decreased oxygen delivery to the kidneys. Situations in which this occurs include insufficient pumping of blood by the heart, lung disease, anemia (a decrease in number of erythrocytes or in hemoglobin concentration), prolonged exercise, and exposure to high altitude. As a result of the increase in erythropoietin secretion, plasma erythropoietin concentration, erythrocyte production, and the oxygen-carrying capacity of the blood all increase. Therefore, oxygen delivery to the tissues returns toward normal. Testosterone, the male sex hormone, also stimulates the release of erythropoietin. This accounts in part for the higher hematocrit in men than in women.
Leucocytes The number of leucocytes or white blood cells (WBCs) per microlitre of blood is called the total leucocyte count (TLC). This varies from 5,000 to 10,000 per cubic millimetre of blood in humans. Rise in WBC count is termed leucocytosis.Abnormal increase of WBCs is in malignancies like leukemia (blood cancer). Fall in WBC count is called leukopenia. They can change their shape like Amoeba and are thus, capable of amoeboid movement. This enables them to squeeze out of blood capillaries into the tissues. This process is called diapedesis. The WBCs are colourless. A leucocyte consists of cell membrane, nucleus and cytoplasm. The cytoplasm
contains mitochondria, Golgi apparatus, centrioles besides other cell organelles. The leucocytes are of two main types : Agranulocytes and granulocytes. In agranulocytes, granules are not found in the cytoplasm. It is of two types, lymphocytes and monocytes. Lymphocytes produce antibodies to destroy microbes. They are non-motile and non-phagocytic. These are B–and T–lymphocytes. Monocytes are the largest of all types of leucocytes. They are motile and phagocytic in nature and engulf bacteria and cellular debris. Granulocytes contain abundant membrane surrounded granules in their cytoplasm. They have multi-lobed nuclei, thus also referred to as polymorphonuclear granulocyte. According to their staining property, the granulocytes are divided into three types, eosinophils, basophils and neutrophils. Eosinophils (1 – 6%) have bilobed nucleus and coarse granules that take acidic stains. They seem to play a role in the immune system. The coarse granules contain hydrolytic enzymes and peroxidase which are discharged into the phagosome. Basophils (0 – 1%) have nucleus which is three lobed and have less number of coarse granules. Their granules take basic stains and release heparin, histamine and serotonin. Neutrophils (40 – 75%) stain equally well with both basic and acidic dyes. They are quite large and have many lobed nucleus and abundant granules. Neutrophils are phagocytic in nature and are the most numerous of all leucocytes. Neutrophils are by for the most abundant kind of leucocytes.
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Thrombocytes (Blood platelets)
There are about 2,50,000 platelets in a cubic millimeter of blood. Increase and decrease in the number of platelets is known as thrombocytosis and thrombocytopenia respectively. The circulating platelets are colourless, non-nucleated cell fragments that contain numerous granules and are much smaller than erythrocytes. Platelets are produced when cytoplasmic portions of large bone marrow cells, termed megakaryocytes, pinch off and enter the circulation. When an injury is caused, the blood platelets release certain chemicals which are called the platelet factors (e.g., thromboplastin). The platelet factors help in the clotting of blood. Numbers and distributions of erythrocytes, leukocytes and platelets in normal human blood 3 Total erythrocytes = 5,000,000 per mm of blood 3 Total leukocytes = 7000 per mm of blood Percentages of total leukocytes: Neutrophils = 50% – 70% Eosinophils = 1% – 4% Basophils = 0.1% – o.3% Monocytes = 2% – 8% Lymphocytes = 20% – 40% 3 Total platelets = 250,000 per mm of blood.
Regulation of blood cell production In children, the marrow of most bones produces blood cells. By adulthood, however, only the bones of the chest, base of the skull, spinal vertebrae, and upper portions of the limbs remain active. The bone marrow in an adult weighs almost as much as the liver, and it produces cells at an enormous rate. All blood cells are descended from a single population of bone marrow cells called pluripotent hematopoietic stem cells, which are undifferentiated cells capable of giving rise to precursors (progenitors) of any of the different blood cells. When a pluripotent stem cell divides, its two daughter cells either remain pluripotent stem cells or become committed to a particular developmental pathway. The first branching yields either lymphoid stem cells, which give rise to the lymphocytes, or myeloid stem cells, the progenitors of all the other varieties. At some point, the proliferating offspring of the myeloid stem cells become committed to differentiating along only one path—for example, into erythrocytes. Proliferation and differentiation of the various progenitor cells is stimulated, at multiple points, by a large number of protein hormones and paracrine agents collectively termed 38
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hematopoietic growth factors (HGFs).Thus, erythropoietin, the hormone described earlier, is an HGF. Table : Major hematopoietic growth factors (HGFs) that stimulates progenitor cells to produce the given cells Name Erythropoietin
Produces Erythrocytes
C o l o n y - s t i m u l a t i n g Granulocytes and monocytes factors (CSFs) Interleukins (example: Various leukocytes interleukin 3) Thrombopoietin
Platelets (from megakaryocytes)
Stem cell factor
Many types of blood cells
HEMOSTASIS: The prevention of blood loss The stoppage of bleeding is known as hemostasis (do not confuse this word with homeostasis). Physiological hemostatic mechanisms are most effective in dealing with injuries in small vessels—arterioles, capillaries, and venules, which are the most common source of bleeding in everyday life. In contrast, the body usually cannot control bleeding from a medium or large artery. When a blood vessel is severed or otherwise injured, its mediate inherent response is to constrict. The mechanism is not completely understood but most likely involves changes in local vasodilator and constrictor substances released by endothelial cells and blood cells. This short-lived response slows the flow of blood in the affected area. In addition, this constriction presses the opposed endothelial surfaces of the vessel together, and this contact induces a stickiness capable of keeping them “glued” together. Stoppage of bleeding ultimately depends upon two interdependent processes that occur in rapid succession: (1) formation of a platelet plug and (2) blood coagulation (clotting). The blood platelets are involved in both processes.
Formation of a platelet plug The involvement of platelets in hemostasis requires their adhesion to a surface. Injury to a vessel disrupts the endothelium and exposes the underlying connective-tissue collagen fibers. Platelets adhere to collagen, by a plasma protein (Von Willebrand factor) secreted by endothelial cells and platelets. This protein binds to a exposed collagen molecules, changes its conformation, and becomes able to bind platelets. Thus, vWF forms a bridge between the damaged vessel wall and the platelets. Binding of platelets to collagen triggers the platelets to release the contents of their secretory vesicles, which contain
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a variety of chemical agents. Many of these agents, including adenosine diphosphate (ADP) and serotonin, then act locally to induce multiple changes in the metabolism, shape, and surface proteins of the platelets, a process called platelet activation. Some of these changes cause new platelets to adhere to the old ones, a positive feedback phenomenon termed platelet aggregation, which rapidly creates a platelet plug inside the vessel. Chemical agents in the platelets’ secretory vesicles are not the only stimulators of platelet activation and aggregation. Adhesion of the platelets rapidly induces them to synthesize thromboxane A2, a member of the eicosanoid family, arachidonic acid in the platelet plasma membrane.Thromboxane A2 is released into the extracellular fluid and acts locally to further stimulate platelet aggregation and release of their secretory vesicle contents. Fibrinogen, a plasma protein plays a crucial role in the platelet aggregation. It does so by forming the bridges between aggregating platelets. The platelet plug can completely seal small breaks in blood vessel walls. Its effectiveness is further enhanced by another property of platelets–contraction. Platelets contain a very high concentration of actin and myosin, which are stimulated to contract in aggregated platelets. This causes compression and strengthening of the platelet plug. The platelet plug is built up very rapidly and is the primary mechanism used to seal breaks in vessel walls. Once started, why the platelet plug does not continuously expand, spread away from the damaged endothelium along intact endothelium in both directions? One important reason involves the ability of the adjacent undamaged endothelial cells to synthesize and release the eicosanoid known as prostacyclin (also termed prostaglandin I2 , PGI2 ), which is a profound inhibitor of platelet aggregation. Thus, whereas platelets possess the enzymes that produce thromboxane A2 from arachidonic acid, normal endothelial cells contain a different enzyme that converts intermediates formed from arachidonic acid not to thromboxane A2 but to prostacyclin. In addition to prostacyclin, the adjacent endothelial cells also release nitric oxide, which is not only a vasodilator but also an inhibitor of platelet adhesion, activation, and aggregation.
Blood coagulation When an injury is caused to a blood vessel, bleeding starts which is stopped by a process called blood clotting or blood coagulation.
At the site of an injury, the blood platelets disintegrate and release a phospholipid, thromboplastin. Injured tissues also release thromboplastin. In response to rupture of the vessel or damage to the blood, a complex cascade of chemical reactions occur. The net result is formation of a complex of activated substances called prothrombin activator. The prothrombin activator catalyzes conversion of prothrombin into thrombin. The thrombin acts as an enzyme to convert fibrinogen into fibrin fibres that enmesh platelets, blood cells, and plasma to form the clot.
The rate-limiting factor in causing blood coagulation is the formation of prothrombin activator, as the terminal steps normally occur rapidly to form the clot itself. The normal clotting time is about 2 to 8 minutes. Prothrombin activator is generally considered to be formed in two ways by the extrinsic pathway that begins with trauma to the vascular wall and surrounding tissues and by the intrinsic pathway that begins in the blood itself. Extrinsic pathway In extrinsic pathway, traumatized tissue releases tissue thromboplastin. The thromboplastin complexes with blood coagulation Factor VII and, in the presence of calcium ions, acts enzymatically on Factor X to form activated Factor X (Xa). The activated Factor X combines immediately with tissues phospholipids released from platelets as well as with Factor V to form the complex called prothrombin activator ++ in the presence of calcium ions (Ca ), this splits prothrombin to form thrombin, and the clotting proceeds. Once clotting begins and thrombin begins to form. The proteolytic action of thrombin activates Factor V. This accelerate prothrombin activation.
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factor. Activated Factor X combines with Factor V and platelet or tissue phospholipids to form the complex called prothrombin activator.
Intrinsic pathway The second mechanism begins with trauma to the blood itself or exposure of the blood to collagen. Blood trauma causes activation of Factor XII and release of platelet phospholipids. When Factor XII comes in contact with collagen or with a wettable surface such as glass, it takes on a new molecular configuration that converts it into a proteolytic enzyme called “activated Factor XII.” The blood trauma also results in release of platelet factor 3. The activated Factor XII activates Factor XI. This reaction also requires HMW (high molecular weight) kininogen and is accelerated by prekallikrein. The activated Factor XI then acts enzymatically on Factor IX to activate this factor. The activated Factor IX together with activated factor VIII and platelet factor 3 from the traumatized platelets activates Factor X. Factor VIII is the factor that is missing in a person who has classic hemophilia, for which reason it is called antihemophilic
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Prothrombin Prothrombin is a plasma protein, an alpha2-globulin, having a molecular weight of 68,700. It is present in normal plasma in a concentration of about 15 mg/dl. It is an unstable protein that can split easily into smaller compounds, one of which is thrombin, which has a molecular weight of 33, 700. Prothrombin is formed by the liver. Vitamin K is required by the liver for normal formation of prothrombin as well as for formation of a few other clotting factors (fibrinogen). In the early stages of polymerization, the fibrin monomer molecules are held together by weak non-covalent hydrogen bonds, and the newly forming fibres are not cross-linked with one another; therefore, the resultant clot is weak and can be broken apart with ease. But in few minutes, process strengthens the fibrin reticulum, which involves a substance called fibrin-stabilizing factor present in normal plasma globulins. Thrombin activates the fibrin-stabilizing factor. Then this activated substance operates as an enzyme to cause covalent bonds between more and more of the fibrin monomer molecules, as well as multiple cross-linkages between adjacent fibrin fibres thus adding strength to the fibrin meshwork.
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The pale yellow fluid formed after blood coagulation is called serum. It lacks all fibrinogen and most of the other clotting factors. Table : Clotting factors in the blood and their synonyms. Clotting factor
Synonyms
I
Fibrinogen
II
Prothrombin
III
Thromboplastin
IV
Calcium
V
Proaccelerin, labile factor, accelerator globin (ACG)
VI
Proconvertin, Serum prothrombin conversion accelerator (SPCA), stable factor
VII
Antihaemophilic factor (AHF), antihaemophilic factor A, Antihaemophilic globulin (AHG)
VIII
Plasma thromboplastin component (PTC); Christmas factor, Antihaemophilic factor B
IX
Stuart-Prower factor
X
Plasma thromboplastin antecedent (PTA), antihaemophilic factor C
XI
Hageman factor, glass factor
XII
Fibrin-stabilizing factor (FSF), Laki-Lorand factor
Blood Groups Blood of human being is grouped into two groups- ABO and Rh groups. Karl Landsteiner reported first time ABO blood groups in human beings. A, B and O blood groups were discovered by Landsteiner (1900) while AB blood group was found out by de Castello and Steini (1902).
ABO blood group ABO grouping is based on the presence or absence of two surface antigens on the RBCs namely A and B. The plasma contains two natural antibodies.
The distribution of antigens and antibodies in the four groups of blood, A, B, AB and O is given in the following table. Table : Human ABO blood groups and their compatibility. Blood group
Antigens in red blood corpuscles
Antibodies in blood plasma
Can give blood to
Can get blood from
A
A
b
A, AB
A, O
B
B
a
B, AB
B, O
AB
AB
None
AB
All
O
None
a, b
All
O
During blood transfusion, the blood corpuscle factor of the donor must be matched with the blood plasma factor of the recipient, otherwise, the blood corpuscles become agglutinated and destroyed. It may be fatal. The persons with blood group O (universal donor) can donate the blood to all the blood groups but can receive blood only from their own group. The persons with blood group AB (universal recepient) can receive the blood from any blood group, but can donate blood only to their own blood group.
Rh blood group Another antigen, the Rh antigen (Rhesus antigen) is also observed on the surface of RBCs of majority of humans. Such individuals are called Rh positive (Rh+ve) and those in whom this antigen is absent are called Rh negative (Rh-ve). Rh-ve person if exposed to Rh+ve blood, will form specific antibodies against the Rh antigens. A special case of Rh incompatibility (mismatching) has been observed between the Rh-ve blood of a pregnant mother with Rh+ve blood of the foetus. Rh antigens of the foetus do not get exposed to the Rh-ve blood of the mother in the first pregnancy as the two bloods are well separated by the placenta. However, during the delivery of the first child, there is a possibility of exposure of the maternal blood to small amounts of the Rh+ve blood from the foetus. In such cases, the mother starts preparing antibodies against Rh antigen in her blood. In case of her subsequent pregnancies, the Rh antibodies from the mother (Rh-ve) can leak into the foetus or could cause severe anaemia and jaundice to the baby. This condition is called erythroblastosis foetalis.
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EXAM SECTION
1. When the skin is cut the blood forms clots. In which order would the components of the blood become involved?
1. Which is the principal cation in the plasma of the blood? (a) Potassium (b) Magnesium (c) Calcium (d) Sodium. (CBSE-PMT 1999, Punjab 2002, 2003, J & K 2003)
First
Last
(a)
Fibrin
Platelet
Red blood cell
Fibrinogen
(b)
Fibrinogen
Red blood cell
Platelet
fibrin
(c)
Platelet
Fibrin
Fibrinogen
Red blood cell
(d)
Platelet
Fibrinogen
Fibrin
Red blood cell
2. Which statement is true for WBC? (a) Non-nucleated (b) In deficiency cancer is caused (c) Manufactured in thymus (d) Can squeeze through blood capillaries. 3. Diapedesis is (a) formation of WBC (c) passage of WBC
(b) formation of pus (d) bursting of WBC.
4. Prothrombin, which helps in clotting of blood, is released by (a) monocytes (b) erythrocytes (c) lymphocytes (d) blood platelets. 5. Which of the following statements about blood transfusion is correct? Blood group B can give blood to (a) blood groups B, AB and receive from group B and O (b) blood group B and receive from group AB (c) blood group O and receive from group B (d) blood groups B, AB and receive from group AB. 6. Anaemia refers to (a) lack of Hb (c) lack of blood
(b) lack of WBCs (d) lack of thrombocytes.
7. Which of the following factor is known as Christmas factor? (a) Factor VIII (b) Factor XII (c) Factor IV (d) Factor IX. 8. Detection of blood groups is done by agglutinisation test using antiserum. According to this method, if the blood shows coagulation with (a) antiserum B, blood group is AB (b) antiserum B, blood group is B (c) antiserum A and B, blood group is O (d) antiserum A, blood group is O. 9. Which of the following is helpful for erythropoiesis? ++ ++ (a) Ca (b) Mg ++ ++ (c) Fe (d) Cu . 10. Which of the following are not true cells in the blood? (a) Platelets (b) Neutrophils (c) Monocytes (d) Basophils. 42
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2. You are required to draw blood from a patient and to keep it in a test tube for analysis of blood corpuscles and plasma. You are also provided with the following four types of test tubes. Which of these will you not use for the purpose? (a) Test tube containing calcium bicarbonate (b) Chilled test tube (c) Test tube containing heparin (d) Test tube containing sodium oxalate. (CBSE-PMT 2004) 3. Which of the following substances, if introduced into the blood stream, would cause coagulation of blood at the site of its introduction? (a) Prothrombin (b) Fibrinogen (c) Thromboplastin (d) Heparin. (CBSE-PMT 2005) 4. A drop of each of the following, is placed separately on four slides. Which of them will not coagulate? (a) Blood serum (b) Sample from the thoracic duct of lymphatic system (c) Whole blood from pulmonary vein (d) Blood plasma. (CBSE-PMT 2007) 5. Globulins contained in human blood plasma are primarily involved in (a) osmotic balance of body fluids (b) oxygen transport in the blood (c) clotting of blood (d) defence mechanisms of body. (CBSE-PMT 2008) 6. The component of blood which prevents its coagulation in the blood vessels is (a) haemoglobin (b) plasma (c) thrombin (d) heparin. (AIIMS 1999, 2007; DPMT 1997; Karnataka 2009; BHU 2008; AFMC 2003) 7. For clotting of blood, which of the following is necessary? (a) Ca and thromboplastin (b) Na and prothrombin (c) Na and K ions (d) Na and thromboplastin. (BHU 1995, 2000; AFMC 2008) 8. The life span of thrombocytes is (a) 4 to 5 weeks (b) 3 to 4 weeks (c) 3 to 7 days (d) none of these. (DPMT 1995; BHU 1996; J & K 1999; Manipal 2002; Punjab 1996)
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9. Heparin is secreted by (a) nervous cell (c) liver cell
(b) blood cell (d) kidney. (BHU 1997, 2005; AFMC 2007)
10. Vitamin K is required for (a) synthesis of prothrombin (b) conversion of prothrombin to thrombin (c) formation of thromboplastin (d) formation of prothrombinase. (BHU 2001; UPCPMT 2009; Punjab 1998) 11. Which proteolytic enzyme induces lysis of fibrin during fibrinolysis? (a) Fibrin (b) Thrombin (c) Plasmin (d) Platelet factor VIII. (UP-CPMT 1995; BHU 2002; Manipal 1995) 12. The leucocytes contain which of the following in large quantity? (a) Basophils (b) Neutrophils (c) Eosinophils (d) Monocytes. (BHU 2004) 13. Which of the following is phagocytic? (a) Monocyte (b) R.B.C (c) Eosinophil (d) Basophil (BHU 2005, 2008) 14. Life span of RBC is (a) 20 days (b) 120 days (c) 100 days (d) 150 days. (BHU 2008; UP-CPMT 1997, 2003; AFMC 2005) 15. Agranulocytes are (a) lymphocytes and monocytes (b) lymphocytes and eosinophils (c) eosinophils and basophils (d) basophils and monocytes. (DPMT 1998; BHU 2000; Punjab 2003) 16. Formation of RBCs in the bone marrow is called (a) haemopoiesis (b) erythropoiesis (c) leucopoiesis (d) all of these. (DPMT 2002; AFMC 2001, 2005, 2007, 2009; Punjab 2000) 17. Which of the following is not phagocytic in nature ? (a) Monocyte (b) Lymphocyte (c) Mast cell (d) Neutrophil. (DPMT 2007) 18. Erythropoietin is formed in (a) kidney (b) liver (c) spleen (d) red bone marrow. (DPMT 2009) 19. Erythrocytes of adult rabbit and other mammals are formed in (a) liver (b) kidney (c) spleen (d) red bone marrow. (UP-CPMT 1994; Manipal 1996, 2006; AFMC 1998)
20. Blood group ‘O’ has (a) antibody and antigen ‘A’ and ‘B’ (b) antibody ‘A’ and ‘B’ but no antigen (c) antigen ‘A’ and ‘B’ but no antibody (d) all of the above. (Manipal 2000; J & K 2003) 21. The largest corpuscles in mammalian blood is (a) monocytes (b) erythrocytes (c) lymphocytes (d) basophils (Manipal 2002) 22. Thrombin indirectly deactivates factor VIII and V via (a) antithrombin II (b) protein C (c) tissue factor pathway inhibtor (d) plasmin. (AMU 1997, 2008) 23. Megakaryocytes are the (a) cells found between the spaces in the lamellae of compact bone tissues (b) cells of bone marrow which give rise to thrombocytes (c) phagocytes found in the lymph (d) another name for thrombocytes. (AMU 1996,1999) 24. Tissue plasminogen activator is used to (a) help in wound healing (b) dissolve clot in blood vessels after heart attack (c) enhancing the action of immune system (d) stimulating the formation of erythrocytes. (AMU 2006) 25. In normal healthy individuals the percentage of adult and fetal haemoglobin, HbA : HbA2 : HbF is (a) 96 : 2 : 2 (b) 45 : 45 : 10 (c) 50 : 45 : 5 (d) 80 : 10 : 10. (AMU 2009) 26. In the extrinsic clotting pathway the active factor VII activates factors (a) X and XI (b) IX and XI (c) IX and X (d) XI and XII. (AMU 2009) 3
27. Number of RBC in man (per mm ) is (a) 5,00,000 (b) 5,000 (c) 5,000,000 (d) 50,000. (AFMC 1996; Punjab 2000) 28. The breaking of haemoglobin into heme and globin takes place in (a) lymphoid tissue (b) liver (c) kidney (d) none of these. (AFMC 2007) 29. pH of blood is (a) greater than 7 (c) less than 7
(b) ranges between 7-8 (d) none of these. (AFMC 2008)
30. Blood plasma contains–% water. (a) 60 (b) 80 (c) 90 (d) 98
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31. The formation of erythrocytes in foetus takes place in (a) liver and spleen (b) red bone marrow (c) blood plasma (d) sarcoplasm. (Karnataka 2003)
37. Both erythrocytes and leucocytes are formed in (a) thymus (b) bone marrow (c) lymph nodes (d) arterial walls. (Odisha 2003, 2009)
32. Match the types of WBC listed in Column I with the shape of nucleus given under Column II. Choose the answer which gives the correct combination of alphabets of the two columns. Column I Column II (Types of WBC) (Shape of nucleus) i. Neutrophils p. Kidney-shaped ii. Eosinophils q. S-shaped iii. Basophils r. 3 to 5 lobes iv. Monocytes s. 2 lobes t. Disc-shaped (i) (ii) (iii) (iv) (a) r t p q (b) t r q s (c) q p t r (d) r s q p (Karnataka 2003)
38. Leucopenia is the condition where (a) leucocytes decrease below 5000 per cubic mm of blood (b) bone marrow is destroyed (c) total number of lymphocyte decreases from 2% to 0.5% (d) leucocytes increases above 6000. (Odisha 2005)
33. Which one of the following statements is correct with regard to the principle of safe blood transfusion? (a) The donor’s red blood corpuscles should not contain antibodies against the recipient’s serum (b) The recipient’s serum should not contain antigens against the donor’s antibodies (c) The recipient’s serum should not contain the antibodies against the red blood corpuscles of the donor (d) The recipient’s red blood corpuscles should not contain antibodies against the donor’s antigen. (Karnataka 2003)
(Odisha 2006)
34. Blood group is due to (a) specific antigen on the surface of WBC (b) specific antibodies on the surface of RBC (c) specific antigen on the surface of RBC (d) type of haemoglobin present in blood (Odisha 2002) 35. In human which of the following is not a factor in blood coagulation pathway ? (a) Calcium ions (b) Serum albumin (c) Prothrombin (d) Proconvertin. (Odisha 2002) 36. Serum is (a) blood without corpuscles (b) blood without fibrinogen (c) blood without fibrinogen & corpuscles (d) otherwise called as plasma. (Odisha 2002, 2004, 2012; J & K 2002) 44
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39. In an accident there is great loss of blood and there is no time to analyse the blood group. Which blood can be safely transferred (a) O and Rh negative (b) O and Rh positive (c) AB and Rh negative (d) AB and Rh positive. (Odisha 2005; J & K 2001) 40. Pernicious anaemia is (a) low RBC count (b) death of WBC (c) destruction of RBC maturation (d) destruction of young RBC.
41. Ringer solution contains + + + – (a) Na + K ions (b) Na + Cl ions + – + + – (c) K + Cl ions (d) Na + K + Cl ions. (Odisha 2006) 42. Which is not the cellular element of blood ? (a) T-cell (b) B-cell (c) Plasma (d) Monocyte. (Odisha 2008) 43. A matured mammalian (RBC) is unusual because (a) it exhibits diapedesis (b) it is colourless (c) it has no nucleus (d) it can change its shape. (Odisha 2009) 44. The haemoglobin content per 100 ml of blood of a normal healthy human adult is (a) 5 - 11 mg (b) 25 - 30 mg (c) 17 - 20 mg (d) 12 - 16 mg. (AIPMT Mains 2010) 45. Which of the following is required for RBC formation? (a) Vit C (b) Vit B12 (c) Folic acid (d) All of these (BHU 2010) 46. In the clotting mechanism pathway thrombin activates factors (a) XI, VIII, V (b) XI, IX, X (c) VIII, X, V (d) IX, VIII, X. (AMU 2010) 47. Blood clotting corpuscle is (a) thrombocyte (b) monocyte (c) lymphocyte (d) erythrocyte. (AFMC 2010; Odisha 2010)
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(c) A = Erythrocyte, B = Basophil, C = Neutrophil and D = Lymphocyte (d) A = Eosinophil, B = Monocyte, C = Neutrophil and D = Lymphocyte (Karnataka 2012)
48. How many heme molecules are present in one molecule of haemoglobin? (a) 1 (b) 2 (c) 3 (d) 4. (AFMC 2010)
49. In which of the following situations, is there a risk factor for children of incurring Erythroblastosis foetalis? (a) Mother is Rh –ve and father is Rh –ve (b) Mother is Rh –ve and father is Rh +ve (c) Mother is Rh +ve and father is Rh +ve (d) Mother is Rh +ve and father is Rh –ve. (Karnataka 2010) 50. When red blood corpuscles containing both A and B antigens are mixed with your blood serum, they agglutinate. Hence your blood group is __________ type. (a) AB (b) O (c) A (d) B. (Karnataka2010) 51. A certain road accident patient with unknown blood group needs immediate blood transfusion. His one doctor friend at once offers his blood. What was the blood group of the donor? (a) Blood group B (b) Blood group AB (c) Blood group O (d) Blood group A. (AIPMT Prelims 2012) 52. Compared to those of humans, the erythrocytes in frog are (a) without nucleus but with haemoglobin (b) nucleated and with haemoglobin (c) very much smaller and fewer (d) nucleated and without haemoglobin. (AIPMT Prelims-2012) 53. Which one of the following human organs is often called the “graveyard” of RBCs? (a) Gall bladder (b) Kidney (c) Spleen (d) Liver. (AIPMT Mains 2012) 54. Study the diagram given below and identify the cells labelled as A, B, C and D, and choose the correct option. C
A
D
B
(a) A = Eosinophil, B = Erythrocyte, C = Neutrophil and D = Basophil (b) A = Eosinophil, B = Lymphocyte, C = Neutrophil and D = Monocyte
55. Select the option having all the correct characteristics.
(AIIMS 2012)
ASSERTION AND REASON The following questions consist of two statements each : assertion (A) and reason (R). To answer these questions, mark the correct alternative as directed below : (a) If both A and R are true and R is the correct explanation of A. (b) If both A and R are true but R is not the correct explanation of A. (c) If A is true but R is false. (d) If both A and R are false. 1. Assertion : The process of clotting can occur in absence of all cellular elements except platelets. Reason : Activated platelets release vitamin K. 2. Assertion : Persons with blood group O are universal donors. Reason : They have no antigens. 3. Assertion : Prothrombin is essential for blood clotting. Reason : Vitamin E is necessary for its synthesis. 4. Assertion : Anaerobic respiration occurs in RBCs. Reason : Cytoplasm of matured mammalian RBC is entirely filled with haemoglobin. 5. Assertion : Neutrophils are non-phagocytic in nature. Reason : The number of neutrophils increases in people with allergic conditions. 6. Assertion : In the early foetus, erythropoiesis takes place in mesodermal cells of the yolk sac. Reason : Normally, in humans, erythropoiesis occurs within spleen or liver.
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SHORT ANSWER TYPE QUESTIONS
Erythrocytes
1. Fill in the blanks. (i) Haemoglobin is a ________ protein which is made up of a protein called ________ and a non-protein group heme. (ii) ________ stimulates the bone marrow to increase the production of RBCs. (iii) ________ serotonin.
release
heparin,
histamine
and
1.
They are smaller, more They are larger, fewer, numerous and longer lived shorter-lived cells than cells than the leucocytes. erythrocytes.
2.
They have a fixed form. They are rounded but can RBCs of man are circular, change their shape. biconcave and enucleated.
3.
They occur only in blood They can escape from vessels. capillaries into the tissues (diapedesis).
4.
They lose cell organelles They retain cell organelles (ER, mitochondria, (ER, mitochondria, ribosomes, ribosomes, centrioles) centrioles). during development.
5.
They have haemoglobin.
(iv) Platelets are formed from the ________. (v) ________ catalyses breakdown of prothrombin into an active protein called thrombin. 2. Differentiate between erythrocytes and leucocytes. 3. What are the three major steps in blood clotting process or blood coagulation? 4. Write the four differences between blood plasma and serum.
ANSWERS
7. Part - I 1. (d)
2. (d)
3. (c)
4. (d)
5. (a)
6. (a)
7. (a)
8. (b)
9. (c)
10. (a)
1. (d)
2. (a)
3. (c)
4. (a)
5. (d)
6. (d)
7. (a)
8. (c)
9. (c)
10. (a)
11. (c)
12. (b) 13. (a)
14. (b)
15. (a)
16. (b)
17. (b) 18. (a)
19. (d)
20. (b)
21. (a)
22. (b) 23. (d)
24. (b)
25. (a)
26. (c)
27. (c)
28. (b)
29. (b)
30. (c)
31. (a)
32. (d)
33. (b)
34. (c)
35. (b)
36. (c)
37. (b)
38. (a)
39. (a)
40. (c)
41. (d)
42. (c)
43. (c)
44. (d)
45. (d)
46. (a)
47. (a)
48. (d)
49. (b)
50. (b)
51. (c)
52. (b)
53. (c)
54. (d)
55. (b)
2. (a)
3. (c)
4. (b)
5. (d)
Part - II
Part - III
They lack haemoglobin.
3. Blood clotting or blood coagulation process can be described under three major steps. −− First step : At the site of an injury, the blood platelets disintegrate and release a phospholipid, called platelet factor-3 (= Platelet thromboplastin). Injured tissues also release a lipoprotein factor called thromboplastin. ++ These two factors combine with calcium ions (Ca ) and certain protein of the blood plasma to form an enzyme called prothrombinase. −− Second step : Prothrombinase catalyzes breakdown of prothrombin (inactive plasma protein) into an active protein called thrombin and some small peptide fragments. −− Third step : Thrombin acts as enzyme and first brings about depolymerization of fibrinogen (a soluble plasma protein) into its monomers. Later thrombin stimulates repolymerization of these monomers into long insoluble fibre-like polymers called fibrin. The thin, long and solid fibres of fibrin form a dense network upon the wound and trap blood corpuscles (RBCs, WBCs and platelets) to form a clot. The clot seals the wound and stops bleeding. 4. Blood plasma
Blood serum
1.
It is the fluid minus blood It is liquid minus clotting corpuscles. elements.
6. (c)
2.
It is faint yellow in colour. It is pale yellow.
Part - IV
3.
It has fibrinogen and other It does not have fibrinogen clotting materials. and other clotting materials.
4.
It takes part in blood It does not take part in clotting. blood clotting.
1. (c)
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Leucocytes
1. (i) conjugate, globin
(ii) Erythropoietin
(iii) Basophils
(iv) megakaryocytes
(v) Prothrombinase
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nn
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Analysis of various PMTs from 2007-2012
5
5
4
4
3
2009
5 4
3
3
2
2
2
1
1
1
AIPMT
AIIMS
BHU
AFMC
AMU
AIPMT
AIIMS
BHU
AFMC
AMU
6
6
5
5
5
4
4
4
3
2012
6
2011
2010
6
6
2008
2007
6
3 2
2
1
1
1
AIIMS
BHU
AFMC
AMU
AIPMT
AIIMS
BHU
Bacterial diseases • Bacteria are microscopic single-celled organisms at least 1 micron long. • Body tissues and systems can be damaged by pathogenic bacteria in two ways - true infections and effects of toxins. • Types of bacterial diseases are typhoid, pneumonia, dysentery, plague, diphtheria, anthrax, tuberculosis, whooping cough, cholera, leprosy and tetanus.
Typhoid (Enteric fever) • Typhoid is a common bacterial disease caused by a rod-like bacterium, Salmonella typhi, which is commonly found in the intestine of man. • Incubation period varies from 1-3 weeks, average 2 weeks. • Typhoid spreads through food and water contaminated
•
• • •
•
AFMC
AMU
AIIMS
BHU
AFMC
AMU
AIPMT
AIIMS
BHU
AFMC
AMU
3
2
AIPMT
AIPMT
with faeces of the patient. House flies may carry the pathogens from the faeces to the food, milk and water. This disease is characterised by the inflammation of ileum and colon, liver and spleen also become enlarged, abdominal pain, pea soup diarrhoea which may become haemorrhagic, constant fever, extreme weakness, vomiting, rash of rose coloured sporst called rose spots on the upper abdomen and sore throat. It is diagnosed by Widal Test. Certain humans function as carriers without suffering from it. Mary Mallon nicknamed Typhoid Mary was a cook by profession and was a typhoid carrier who continued to spread typhoid for several years through the food she prepared. TAB vaccine provide immunity for about 3 years.
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Pneumonia
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• Pneumonia is caused by Streptococcus pneumoniae or Diplococcus pneumoniae, and Haemophilus influenzae, having an incubation period of 1-3 days. • It is a serious disease of lungs characterised by accumulation of mucus/fluid in alveoli and bronchioles to that extent that breathing becomes difficult. • A healthy person acquires the infection by inhaling the droplets/aerosols released by an infected person or even by sharing glasses and utensils with an infected person. • Pneumonia is of two types : –– Lobar pneumonia affects whole lobes and is usually caused by Streptococcus pneumoniae. –– Lobular pneumonia refers to multiple patchy shadows in a localized or segmental area. When these multiple shadows are widespread, the term bronchopneumonia is used. In this the infection starts in bronchi and spreads in a patchy manner into the alveoli. • The onset of pneumonia is usually sudden with a single shaking chill, followed by fever, pain with breathing on the side of lung involved, increased pulse and respiratory rates and cough. • In severe cases the lips and finger nails turn grey to bluish in colour.
Dysentery • Dysentery is an infection of the intestinal tract causing severe diarrhoea with blood and mucus. • Amoebic dysentery (amoebiasis) is caused by the protozoan Entamoeba histolytica. • Bacillary dysentery is caused by bacteria such as Shigella dysenteriae, Escherichia coli, Campylobacter and Salmonella and is spread by contact with a patient or carrier or through food or water contaminated by their faeces. • Epidemics are common in overcrowded insanitary conditions. • Symptoms, which develop 1-6 days after infection, include diarrhoea, nausea, cramp, and fever and they persist for about a week. • An attack may vary from mild diarrhoea to an acute infection causing serious dehydration and bleeding from the gut. • In most cases, provided fluid 50
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losses are replaced, recovery occurs within 7-10 days; antibiotics may be given to eliminate the bacteria.
Plague (Black death) • Plague is caused by a rod shaped non-motile bacterium called Pasteurella/Yersinia pestis and is transmitted by the bite of infected rat flea, Xenopsylla cheopis. • Pasteurella pestis is endoparasite of gut of rat flea (which is an ectoparasite of rat and mouse). • Head louse (Pediculus) and bedbug (Cimex) may also transmit the germ from man to man. • It is of 3 types–bubonic plague, septicemic plague and pneumonic plague. • Bubonic plague (black death) has an incubation period of 2 - 6 days. Pathogen multiplies in lymph nodes, especially armpit and groin which swell up into painful buboes. • Other symptoms are high fever, chill, delirium, exhaustion and haemorrhages which turn black. The patient dies thereafter. Hence, plague is also called black death. • Plague reached India for the first time in 1895 from Hong Kong. • In septicemic plague buboes do not occur. It is characterised by sepsis, severe headchae, rapid pulse, fever, chill, nausea, vomiting and delirium leading to death within two days. • Pneumatic or pneumonic plague infects lungs causing pulmonary oedema, fever, anoxia, delirium and death within 24 hours. • Anti-plague vaccine, spray of insecticides, killing of rats, and high cots (rat flea can jump upto 45 cm) are some preventive measures. • Plague is confirmed by Wayson stain test.
Diphtheria • Diphtheria is an acute infectious disease of mostly children characterized by the development of a grey adherent false membrane over the upper respiratory tract or throat. • It is caused by toxigenic strains of Corynebacterium diphtheriae (Gram +ve bacterium). • Incubation period is of 2-5 days. • Endotoxin produced by pathogen causes nasal diphtheria, pharyngeal diphtheria and laryngotracheal diphtheria. • Symptoms are fever, sore
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•
• •
• • •
throat, sometimes vomiting, headache, epithelial necrosis by endotoxin and oozing of semisolid material in the throat which develops into a grey false but tough membrane. The membrane chokes the air passage. Sometimes, bacterium infects the heart leading to fatal heart blockage. In severe cases, respiratory tract is blocked causing difficulty in breathing and even death due to choking. The germs are present in the discharges from the nose and throat of patients and also of healthy people who act as the “carriers”. The patients and the carriers spread the disease through acts like kissing, talking, coughing and sneezing. DPT vaccine - diphtheria, pertussis and tetanus vaccine is given as immunization within six weeks of birth. ‘Schick test’ tests the presence of antitoxin and the state of hypersensitivity to diphtheria toxin.
• Pulmonary anthrax is acquired by inhaling dust containing B. anthracis. • Initial symptoms resemble those of common cold. Later there is difficulty in breathing, cough, fever, fast pulse and cardiovascular collapse. • Pulmonary anthrax is often called wool-sorter’s disease. • If left untreated, anthrax in all forms can lead to septicemia and death. • Death is apparently due to oxygen depletion, secondary shock, increased vascular permeability, respiratory failure and cardiac failure. • Bacillus anthracis can be easily grown in the laboratory. Anthrax spores can be produced in a dry form which can be stored as particles. • These particles can be used in biological warfare. Spores are infective in dry form, not in wet form.
Anthrax (Biowar disease)
Tuberculosis
• Anthrax is an acute infectious disease caused by air-borne, spore-forming, rod-like, nonmotile bacterium, Bacillus anthracis.
• Tuberculosis (TB), also called Koch’s disease is caused by rod shaped Gram +ve bacteria, Mycobacterium tuberculosis. • The bacterium releases a toxin, tuberculin which destroys the organs it infects. • It affects the lungs, lymph nodes, bones and joints. • It spreads through sneezing, coughing, contaminated food and water. • Incubation period is 3 to 6 weeks or may be years. • Constant cough and in severe cases sputum with blood, pain in chest while coughing, loss of body weight, failure of appetite, slight rise of temperature in the evening are the symptoms of lung T. B. • BCG (Bacillus Calmette Guerin) vaccine for TB was obtained from bovine bacillus by Calmette and Guerin in 1921. • Sputum, tuberculin, X-ray and gastric analysis are carried out to diagnose tuberculosis. • Tuberculin test is also called Mantoux test. • Direct observation treatment (DOT) is a programme under WHO for treatment of TB across the world.
• It most commonly occurs in wild and domestic lower vertebrates (cattle, sheep, goats, camels, antelopes, and other herbivores), but it can also occur in humans when they are exposed to infected animals or tissues from infected animals. • Infected animals shed in the discharges from the mouth, nose and rectum a large number of bacilli (bacteria) which sporulate in the soil. These spores are source of infection. • It requires thousands of spores to cause human infection. Anthrax does not spread from human to human. • Anthrax infection can occur in three forms: cutaneous (skin), gastrointestinal (by ingestion) and pulmonary (by inhalation). • In cutaneous anthrax bacteria enter through skin cuts and wounds. • A skin lesion begins as a papule and soon becomes a vesicle and breaks, discharging bloody serum. • The seat of this vesicle, in about 36 hours, becomes a bluish-black necrotic mass (dead tissue). It consists of minute particles rich in spores. • Gastrointestinal anthrax is caused by taking undercooked meat of infected animals. • Patient experiences chill, high fever, body aches, nausea, vomiting, bloody diarrhoea, loss of appetite, and frequently haemorrhages from the mucous membranes and in the skin.
Whooping cough (Pertussis) • Whooping cough is caused by Bordetella pertussis and is a common childhood disease affecting the respiratory system. • It spreads by droplet infection or by direct contact. • It has an incubation period of 10 - 16 days. • It causes constant cough leaving the child breathless, tired and red in face. • Later the voice becomes hoarse and the cough gives a whoop or a loud crowing sound while inhaling.
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• The child usually vomits and there is frothy discharge from his mouth and nose. • There may be complications like vomiting, convulsions and pneumonia. • Immunisation of the disease is done by DPT vaccination.
Cholera • Cholera commonly called haiza is a water-borne disease caused by the bacterium, Vibrio cholerae. • Robert Koch discovered this disease. • Incubation period varies from a few hours to 2–3 days. • It spreads through contaminated food and drinks. • The causative bacterium secretes cholera toxin, enterotoxin which induces excessive secretion of an isotonic electrolyte solution by the intestinal mucosa. This solution is lost in stool. • Cholera is mainly characterized by sudden onset of profuse, effortless, rice-water like stools, vomiting and rapid dehydration, loss of minerals and muscular cramps. • Fluid and salt lost is restored by oral rehydration solution (ORS). It is water with a small amount of sugar and salt. • Cholera vaccine is effective for six months only. • Proper sanitation and hygienic conditions are the best methods of prevention.
Leprosy (Hansen’s disease) • Leprosy is a contagious chronic bacterial disease caused by Mycobacterium leprae which is characterised by the chronic infection of the skin and other tissues. • The incubation period is very long and averages 2-5 years. • Infection occurs by prolonged contact with leprosy patients. • The bacilli leave the body in nasal discharge, from the throat during coughing, sneezing and even speaking and through broken skin lesions. • Symptoms of leprosy include appearance of light coloured patches on the skin, thickening of the nerves, partial or total loss of sensation in the affected parts of the body. • These are accompanied by fever, pain, ulcers and skin eruptions. Deformities of toes and fingers may also develop. • It is of two types : tuberculoid leprosy involving tuberculoid granulosus formed by aggregation of macrophages and lepromatous leprosy characterised by nodular aggregates of lipid laden macrophages, lepra cells. • Presence of lepromin in skin test can indicate the appearance of leprosy. 52
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• Tuberculoid leprosy gives positive test with lepromin while lepromatous leprosy is negative to lepromin test. • Leprosy is curable. No vaccine is available
Tetanus (Lock jaw) • Lock jaw disease is caused by the spores of Clostridium tetani that enter through wounds. • Its infection is acquired by contamination of wounds with tetanus spores as these infected spores are abundant in the soil manured with animal dung. • Spores may survive for 60 or more years in contaminated soil. • Incubation period is of 3-25 days during which the bacterium secretes a powerful exotoxin tenanospasmin into the tissue, and blood carries it to the central nervous system and brings about tetanus of muscles. • The symptoms are painful muscular spasms especially of neck and jaw. • Lock jaw condition occurs when the patient cannot open the mouth, convulsions and paralysis of muscles, difficulty in chewing and swallowing, fever and headache also occur. • All wounds should be treated carefully and cleaned with iodine solution. Tetanus toxoid injection should be administered in case of an injury. • Immunisation of infants by DPT or triple vaccine helps in immunity against diphtheria, pertussis and tetanus.
Protozoan diseases • Protozoans are diverse group of eukaryotic, unicellular organisms. • Human diseases caused by protozoa are relatively few, but are individually of devastating consequences. • Types of protozoan diseases are amoebiasis, malaria, African sleeping sickness, kala-azar, ciliary dysentery etc.
Amoebiasis or Amoebic dysentery • Amoebiasis is a protozoan infestation of upper part of large intestine which is caused by monogenetic protozoan (having one host) known as Entamoeba histolytica. • There is one host i.e., man. • The infection occurs by the cysts of Entamoeba present in the stool of infected person. • Inside the intestine, the cyst germinates and releases 4-8 Entamoebae where they secrete an enzyme called cytolysin. • The enzyme partially dissolves the wall of large intestine. • The feeding stage of parasite is called trophozoite or magna. It stops feeding prior to cyst formation.
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• The nonfeeding pre-cystic stage is called minuta form. • Amoebiasis results in ulceration of the intestines and occasionally in the formation of abscesses in the liver (amoebic or tropical abscesses), lungs, testes, or brain. • Symptoms appear days or even years after infection and include pain in abdomen, diarrhoea, indigestion, loss of weight, and anaemia. • To prevent the infection, the sanitary disposal of faecal matter and cleanliness in the preparation of food should be carefully done.
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Malaria • Malaria is caused by a digenetic (have two hosts to complete its life cycle) and triphasic (having three phases of life cycle) protozoan parasite known as Plasmodium. • The primary host is female Anopheles mosquito and secondary host is man. • Sir Ronald Ross (1897), a doctor in Indian Army, established that malarial parasite is transmitted by the bite of a female Anopheles mosquito for which he got Nobel Prize in 1902. • The malarial parasite, Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. • The sporozoites reach the liver cells via blood where they initially multiply. These then attack the red blood cells (RBCs) resulting in their rupturing. • The rupture of RBC is associated with the release of haemozoin, a toxin which causes the chill and high recurring fever every three to four days. • The female Anopheles mosquito when bites an infected human being, the malarial parasites enter into the mosquito’s body and undergo further development to form sporozoites that finally move to the salivary glands of the insect. • The bite of these mosquitoes introduces the sporozoites inside the body, thus initiating the above mentioned cyclic process again. • The attack of malaria is preceeded by yawning, tiredness, headache and muscular pain. • There are four species of Plasmodium which causes four main types of malaria in human. They are –– Plasmodium vivax : Benign tertian malaria in which fever recurs after every 48 hours. –– P. malariae : Quartan malaria in which fever appears after every 72 hours, and often produces persistent subclinical malaria. –– P. falciparum : Cerebral malaria or malignant tertian malaria where fever recurs after every 48 hours.
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–– P. ovale : Causes mild tertian malaria. The incubation period of Plasmodium ovale and P. vivax is about 14 days, 12 days for P. falciparum and 28 - 30 days for P. malariae. Black water fever caused by infection of P. falciparum results in the excretion of haemoglobin in urine. Malaria is characterised by fever at intervals, sudden acute chilliness (cold or rigor stage) accompanied by shivering followed by rise in temperature. Peak fever (hot or febrile stage) is 41.1°C or 106°F which persists for 3-6 hours. After 2-4 hours of fever, there is profuse sweating (sweating or defervescent stage) which lowers the body temperature to near normal. Malaria is also accompanied by nausea, headache, laziness and muscular pains. It also results in anaemia and splenomegaly. Clinical fever in malaria is due to erythrocytic schizogony. Drugs like chloroquin and primaquin are administered to treat malaria. Other drugs like quinine obtained from the bark of Cinchona plant, camoquin, daraprim and artemesenin obtained from Artemesia annua (is effective against cerebral malaria) are also used to treat malaria. Spreading areas with DDT, BHC and other insecticides. introducing Utricularia, ducks and larva eating fishes like Gambusia, stickle back minnow and trout in larger water reservoirs, putting oil (kerosene) in the water ponds can help to protect against the breeding of mosquitoes.
African sleeping sickness (Trypanosomiasis) • Trypanosoma is a flagellate protozoan whose different species causes different types of trypanosomiasis. • It is of two types : –– Gambian (W. African) sleeping sickness caused by Trypanosoma gambiense by the bite of the blood sucking tse tse fly, Glossina palpalis. –– Rhodesian (E. African) sleeping sickness caused by Trypanosoma rhodesiense by the bite of the tse tse fly, Glossina palpalis and Glossina morsitans. • Trypanosoma is a protozoan which is digenetic having two hosts : –– Primary host : man. –– Antelope as reservoir host. –– Secondary host : tse tse fly, Glossina palpalis. • The parasite lives in the blood stream and in the lymph, it invades the cerebrospinal fluid of the CNS causing fever, anaemia, lethargy and death. • The infection is initiated by the bite of tse tse fly which harbours the infective metacyclic forms in the lumen of its salivary glands.
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• This disease is characterised by swelling of lymphatic glands, irregular recurrent fever followed by weakness, loss of weight, anaemia, increase in pulse rate and severe headache. • Chaga’s disease (South American sleeping sickness) is caused by Trypanosoma cruzi which spreads by the faeces of triatomid bugs.
• Protection of food articles from dust and flies that may carry cysts is the best prevention from infection.
Kala-azar (Dumdum fever or Visceral leishmaniasis)
• It inhabits upper part of small intestine (duodenum and jejunum).
• Kala-azar also known as Black fever or Dumdum fever, is caused by the protozoan Leishmania donovani through the bite of the sand fly, Phlebotomus. • Its primary host is man and secondary host is sand fly while reservoir hosts are dogs and cats. • Incubation period is long from 3 to 6 months, and symptoms may appear even after 2 years. • Early symptoms of kala-azar include swelling, high fever and enlargement of spleen and liver, followed by general weakness, emaciation, anaemia due to reduction in number of blood cells, and a peculiar darkening of skin. • In advanced stage hair becomes brittle and falls out. The body immune system becomes so weak that secondary infections by bacteria or viruses lead to death. • Eradication of the insect vector sandfly by insecticides, eliminating the reservoir hosts, and avoiding the bite of sandfly are the prophylactic measures against kala-azar. • Other leishmanial diseases of man are : –– Oriental sores (skin lesions) : Leishmania tropica. –– Naso-pharyngeal leishmaniasis : Leishmania brasiliensis or Espundia. –– South American kala-azar : Leishmania chagasi.
Ciliary dysentery (Balantidiasis) • Ciliary dysentery is caused by ciliated protozoan named Balantidium coli. • The protozoan inhabits the human large intestine (colon). It is also seen in pigs and monkeys. In pigs they are nonpathogenic. • It reproduces asexually by transverse binary fission and sexually by conjugation. The latter is followed by cyst formation. Cysts pass out in the host’s faeces. • Infection occurs by ingesting cysts with food and drinks. • The protozoan causes ulcers in the colon and invades mucous membrane by secreting an enzyme hyaluronidase. • This generally results in vomiting, abdominal pain, weight loss and diarrhoea, but may also lead to severe or fatal dysentery. 54
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Giardiasis • Giardiasis is a protozoan disease caused by Giardia intestinalis, ‘The Grand Old Man of the intestine’. • It is the first human parasitic protozoan known.
• Infection occurs by contamination of food and drink with cyst. • It is characterised by epigastric pain, abdominal discomfort, headache, diarrhoea and sometimes fever. • Clean water supply, infection free food, properly washing hands, fruits and vegetables before eating etc. are some of the preventive measures.
Helminthic diseases • Helminths are animals that belong to the phyla Platyhelminthes and Nematoda (Nemathelminthes). • Many parasitic forms of this group, popularly known as parasitic worms, are endoparasites of gut and blood in human body which cause various diseases.
Ascariasis • Common ascariasis is caused by the common round worm Ascaris lumbricoides. It is a giant intestinal worm, white in colour and female longer than the male. • Female lays about 200,000 eggs daily that passout with human faeces and remain alive in the soil for several days. • It is an endoparasite of the small intestine of human beings. • It is more common in the children, because the latter are generally in the habit of eating soil and clay, which may be infected by the eggs of Ascaris. • Since a large number of adult Ascaris worms normally infest a single host, they obstruct the intestinal passage and thereby cause abdominal discomfort, like colic pains. • The patient may also suffer from impaired digestion, diarrohea and vomiting. • Worms sometimes bore the intestinal epithelium and lead to some vital organs like kidneys, spinal cord, brain or muscles causing injuries to the organs. • Worm produces toxins which cause irritation of mucous membranes, convulsions, nervousness etc. • The parents should see to it that their children do not take to the habit of eating soil.
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Taeniasis • It is caused by Taenia solium (Pork tape worm). • The adults of T. solium are parasites in the small intestine of human beings (primary host) and its larva infests the muscles of the pig mostly (secondary host). • Taeniasis can be recognised by such symptoms as abdominal pain, restlessness, anaemia, insomnia, and loss of appetite (anorexia) coupled with indigestion. • While the hooks and suckers cause mechanical obstruction in the intestine and the toxin released by the tapeworm brings about the above-mentioned disorders. • The pork should be fully cooked before eating and the faecal matter of infected human beings should be destroyed in pits.
Cysticercosis • It is caused by cysticercus (a larva of tape worm). Cysticercus is more dangerous than Taenia solium. • Cysticercus develops from another larva called onchosphere. The onchospheres reach the intestine where they develop into cysticerci. • These cysticerci reach the eyes where they may undergo encystment and cause blindness or they can cause epilepsy in the brain. Hydatid disease • It is caused by Echinococcus granulosus (the dog tapeworm or hydatid worm). It lives as an endoparasite in the intestine of dogs, cats and foxes, etc. • Man sometimes serves as an incidental host. Man acquires infection by playing with pet dogs. • The parasite liberates toxins which have harmful effect on the body and brain of the host.
Filariasis or elephantiasis • The disease is due to nematode Wuchereria bancrofti (= Wuchereria = Filaria). Another species is W. malayi. • The pathogen is spread from one human being to another through mosquitoes like Culex and to a lesser extent by Anopheles and Aedes. • The parasite resides in lymph vessels, connective tissues and mesentery. • The parasite is viviparous. The young ones are called microfilariae. They are hardly 2.5 mm long. • Microfilariae enter the blood vessels and reach the skin area during night (8 pm to 4 am) for being picked by female mosquito for completion of life history and changing into infective stages. • The infective parasites are deposited near the site of
mosquito bite. They pass through the punctured skin and reach the lymphatic system. • The disease passes through four stages in human beings: (i) In the first stage, the patient has increased eosinosphils, enlarged lymph nodes and positive intradermal parasite test. (ii) Second or carrier stage is symptomless but the right blood examination can reveal the parasite. (iii) Third stage is characterised by filarial fever, inflammation of lymph nodes (lymphadenitis) and lymph vessels (lymphangiectasis) and reversible lymphoedema (excess fluid in tissues due to obstruction of lymph vessels) in various body parts. (iv) The fourth or final stage is manifestated by lymphoedema accompanied by thickening of subcutaneous tissues and skin so that there is permanent swelling mostly of feet, legs, thighs, scrotal sacs, breast etc. It is called elephantiasis.
Ancylostomiasis (Hookworm disease) • Ancylostomiasis is caused by hook worm Ancylostoma duodenale which is the parasite of the intestine. • Man acquires infection when eggs hatch and juveniles penetrate through soft skin of hands and feet. • They enter the blood vessels and carried to heart and lungs finally reaching the intestine where they develop into adult worms. • Gastro-intestinal disturbances, anaemia and nervous disorders are the characteristics of the disease. • Patient appear pale and weak, nausea and vomiting are also frequent. In severe cases, men become impotent and women cease to menstruate.
Enterobiasis (Oxyuriasis) • This disease is caused by Enterobius vermicularis (pinworm). • It is found in human caecum, colon or vermiform appendix. It is more common in children. • Fertilized females make trips to the anus of the host to lay eggs. Eggs are deposited on the perianal region. • The patient scratches the affected area. The eggs easily get under the finger nails from where they may get into the mouth. • The eggs may infect the other members of the family through clothes, dust, air and furniture in the room. • The disease causes intense itching of the anus, inflammation of mucous membrane of colon and appendix, and nausea, abdominal pain and diarrhoea. • No intermediate host is required to complete the life cycle. Thus, its life cycle is monogenetic.
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Trichinosis
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• It is caused by Trichinella spiralis. • Adult worm lives as an endoparasite in human intestine and some other mammals like pig, dog, cat, rat, however, its larvae are present in striated muscles of the host. • Nausea, vomiting, oedema of face and eyelids, fever, muscular pain, pain in chewing, swallowing, breathing and in moving arms and legs.
Trichuriasis • It is caused by Trichuris trichuria, a whip worm. • Eggs of the worm gain entry to human body with contaminated drinking water, raw fruits and vegetables. • In intestine the eggs hatch and larva develop into adult whip-worms. • Nausea, vomiting, constipation, headchae, slight fever, pains resembling appendicitis, anaemia and eosinophilia are its symptoms.
Dracunculiasis • This disease is caused by Dracunculus medinensis (guinea worm) that occurs in the subcutaneous tissue of man. • The parasite produces toxic secretions which cause a blister on the skin of the man. • When the host comes in contact with cold water, the female worm found below the skin, releases larvae in the water. • The larvae penetrate the body of cyclops, a fresh water crustacean, which is the intermediate host of the guinea worm. • When the infected cyclops is taken in by man with water, the larvae escape from the cyclops into the human intestine. • The larvae bore their way to the subcutaneous tissue where they become adults. • The guinea worm causes itching, diarrhoea, nausea, vomiting and eosinophilia due to its toxic secretions in the human body. Loiasis • This disease is caused by Loa loa (the eye worm) which lives in the subdermal connective tissue of man and baboons in some parts of Africa. • Man gets infection by bites of infected deerfly chrysops. • The disease is characterised by subcutaneous swelling (called calabar swelling) mostly around the eyes. Opisthorchiasis (= Clonorchiasis) • This disease is caused by Opisthorchis (= Clonorchis) sinensis which inhabits the bile ducts. 56
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• Humans are infected through eating raw or under-cooked fish which harbour metacercariae. • Adult flukes are found in biliary ducts, causing the thickening of duct walls, and it also causes cirrhosis and ultimately death. • All freshwater fishes should be thoroughly cooked before eating. Fasciolopsiasis • This disease is caused by the intestinal fluke Fasciolopsis fuelleborni in India. Snail acts as the intermediate host of this parasite. • Infection is by eating infected water plants, particularly the water nuts, with metacercariae larvae. • The worms cause erosion of intestine lining causing bleeding and pain. Diarrhoea, nausea and vomiting followed later.
Schistosomiasis • Blood flukes Schistosoma mansoni, S. japonicum and S. haematobium causes this disease. • Infection is through the penetration of skin of man by the cercariae larvae which swim freely in water. Then they reach the lung and develop into adult which then live in the blood stream. • Blood flukes cause asthmatic attacks and hepatitis, fever, sweating, diarrhoea, weight loss and lack of appetite follow later on. • Sanitary disposal of all human faeces and urine are the preventive measures.
Paragonimiasis • This disease is caused by the lung fluke, Paragonimus westermani, found in lungs in encapsulated form. • Man acquires infection from eating raw or under cooked crabs and crayfish infected with cercariae larvae. • They cause chronic cough with emission of bloody sputum. Heavy infections cause chest pain with pleurisy, shortness of breath, fever and anaemia.
Fungal Disease Dermatophytosis (Ring worm, Tinea) • Dermatophytosis is caused by the group of fungi, dermatophytes. • The dermatophytes are closely related filamentous fungi that infect only superficial keratinised tissues–the skin, hair and nail. They are popularly called ringworm or tinea. • Dermatophytes have been classified into three genera– Trichophyton, Microsporium and Epidermophyton.
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• Trichophyton : Trichophytons infect skin, hair and nails. T. rubrum is the most common species infecting man. • Microsporum : It infects the hair and skin but usually not the nails, e.g., M. canis. • Epidermophyton : It attacks the skin and nails but not the hair, e.g., E. floccsum. • Clinically, ringworm can be classified according to the affected parts such as (i) Tinea pedis (athletes’ foot) is ringworm of the foot. (ii) Tinea capitis – ringworm of the scalp. (iii) Tinea cruris – involvement of the groin and perineum. (iv) Tinea barbae – involvement of the bearded areas of the face and neck.
Non communicable diseases • The non-communicable diseases remained confined to the persons who suffer from them. • These are not transmitted from infected persons to other persons. Some important non-communicable diseases are described here.
Diabetes mellitus (Hyperglycemia) • The most common endocrine disorder of the pancreas is the diabetes mellitus, now recognised to exist in two forms– Insulin-dependent and non-insulin-dependent. • The insulin-dependent diabetes mellitus (IDDM) is caused by a failure of the Beta-cells to produce adequate amounts of insulin while the non-insulin-dependent diabetes mellitus (NIDDM) appears to involve failure of insulin to facilitate the movement of glucose into cells. • In both disorders the blood glucose concentration is elevated above the normal range. • Some of the glucose is excreted in the urine, and water follows the glucose, causing excessive urination and dehydration of body tissues. • This causes frequent drinking because of extreme thirst (polydipsia). • The cells are unable to utilize glucose and other carbohydrates for energy production. They utilize their proteins for it. The person becomes very weak. • Degradation of fats increases, producing ketone bodies (ketosis). The latter are acidic and poisonous, • Blood cholesterol level rises. Healing power is impaired. Administration of insulin lowers the blood-glucose level. It gives relief to the patient.
Table : Differences between Type I and Type II Diabetes NIDDM (Type II)
IDDM (Type I)Juvenile Diabetes 1.
Onset less than 20 years. Onset more than 30 years.
2.
Normal weight.
Obese.
3.
Ketoacidosis common
Ketoacidosis rare.
4.
Severe insulin deficiency. Relative insulin deficiency.
5.
Beta-cell depletion.
Mild beta-cell depletion.
Cardiovascular diseases • The diseases that affect the blood vessels and the heart are called cardiovascular diseases. These are as follows : Hypertensive heart diseases • Arteriosclerosis : Hardening and loss of elasticity of the arteries is commonly referred to as arteriosclerosis. It causes hypertension or high blood pressure. • Atherosclerosis : In this disease a lumpy thickness develops on the inner walls of the arteries that prevents the dilation of vessels (arteries). Hypertension (High blood pressure) • It is defined as a resting arterial pressure exceeding 120/80 over a prolonged period of time. • Disorders that can result from untreated hypertension include heart failure, kidney damage and cerebro-vascular accident (rupture of a cerebral artery sometimes called a stroke). • Dietary sodium is sometimes restricted. Coronary heart diseases • Coronary heart diseases include : (i) Angina pectoris • Sclerosis of the coronary arteries can cause “pain in the chest”. • This anginal pain usually starts in the centre of the chest and spreads down the left arm. • The chest pain may be associated with restlessness, fear or anxiety, a pale skin, profuse sweating and vomiting. • The pain lasts for only a few moments. (ii) Coronary thrombosis or Myocardial infarction (MI) • A clot may form in the lumen of a coronary artery, it is called coronary thrombosis.
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• Therefore, a large portion of the heart muscle is deprived of blood and the patient develops a “heart attack”.
Rheumatic heart disease (RHD) • This is the more frequent cardiovascular disease in India below the age of 20 years. • The patient may have an acute rheumatic fever, joint pains and infection of throat. • Rheumatic fever may cause permanent damage of one or more valves (mitral or aortic semilunar valves), pericarditis and myocarditis. • Its causative factor is Streptococcus bacteria. • Recently, Coxsackie B-4 virus has been suggested as a conditioning agent. • The risk of acute rheumatic fever is greatest where there is bad housing, overcrowding and inadequate conditions of hygiene. • RHD is called poor persons’ disease. Stroke (Cerebrovascular Accident or CVA) • It is the sudden interruption of blood flow to a portion of the brain because of block or rupture of a cerebral blood vessel. • Thus, the brain cells do not get oxygen and glucose. This can cause paralysis, loss of speech, etc. Arthritis or Aching joints • Arthritis is not just one disease but a general term that can be applied to as many as twenty-five malfunctions of the joints. • Some important types of arthritis are as follows : • Rheumatoid arthritis (RA) is the most common arthritic disease. • Rheumatoid arthritis is an inflammation of the synovial membrane in synovial joints. • When this membrane, which is the source of synovial fluid, becomes inflamed, it produces too much fluid. The joints swell and become extremely painful. • In response to the inflammation and swelling, a hard tissue forms over the cartilage articulations. This tissue makes the joint stiff. Movement then becomes more painful. • In a course of time, the new tissue can grind away the entire cartilage. When this happens, the two bones fuse and the joint becomes totally immovable. • Several joints are affected. RA 58
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is result of auto-immune reaction. • Osteoarthritis (osteo-bone) affects only the cartilage at synovial joints. • From years of use, the cartilage erodes and new bone is deposited in lumps. • The lumps make movement difficult and finally impossible. • Many people who suffer this form of arthritis have no pain, but their fingers may curl and permanently arch and their wrists and other joints may display lumps of bone formation. • Gout is another form of arthritis related to diet. • In fact, gout is the accumulation of uric acid crystals in synovial joints. • The accumulation makes movement both difficult and painful. • Uric acid, a byproduct of protein metabolism is normally excreted in the urine. • Gout sufferers should avoid meat, particularly liver, kidney, brain, thymus gland, and other glands.
Cancer • Cancer or malignant neoplasm is a disease of uncontrolled proliferation of cells without any differentiation. • The cancer cells invade and destroy the surrounding tissues. • Due to uncontrolled divisions, an abnormal growth called tumour occurs. • Tumour or neoplasm is any abnormal swelling, lump or mass in the body. Neoplasm or tumour is of two types : • Benign tumour (= Nonmalignant tumour) : It remains confined to the site of its origin and does not spread to other parts of the body. It causes limited damage to the body. It is non-cancerous. • Malignant tumour : This is the actual cancerous tumour which grows and invade other tissues showing the metastasis.
Types of cancers •
Cancers are classified on the basis of the tissue from where they arose. Carcinomas • This type is mainly derived from epithelial cells. • They include cervical (cervix is part of uterus) cancer, breast cancer, skin cancer, lung cancer, stomach cancer, etc. • About 80% of all tumours are carcinomas.
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Leukaemias • Leukaemias are commonly called as blood cancers. Leukaemias result from excessive formation of WBCs in the bone marrow and lymphatic nodes. Lymphomas • Lymphomas are the cancers of the lymphatic tissues. • Hodgkin’s disease is an example of human lymphoma. In this there is chronic enlargement of the lymph nodes and spleen. • There is excessive production of lymphocytes by lymph nodes and spleen. Germ cell tumour • These tumours are derived from totipotent cells found. • Found in adults most often in the testicle and ovary. Blastic tumour • A tumour which resembles an immature or embryonic tissue. Many of these tumours are most common in children. Myeloma (Multiple myeloma or Kahler’s disease) • It is a type of cancer of plasma cells (B-lymphocytes) which are immune system cells in bone marrow that produce antibodies. Causes of cancer • Chemical and physical agents that can cause cancer are called carcinogens. Carcinogens fall into three basic categories. • Oncogenic transformation: They are the carcinogens
which bring about changes in genetic material. They are of two types, radiations and chemicals. • Tumour promoters: They promote proliferation of cells which have undergone oncogenic transformation, e.g., some growth factors, hormones etc. • Tumour viruses: Some viruses are known to involve in oncogenic transformations. Possible symptoms of cancer (i) A persistent cough or hoarseness in a smoker. (ii) A peristent change in digestive and bowel habits. (iii) A change in a wart or mole. (iv) A lump or hard area in the breast. (v) Unexpected diminished or lost appetite. (vi) Unexplained low-grade fever. (vii) Unexplained loss of weight. (viii) Any uncurable ulcer. (ix) Bleeding in vagina at times other than the menstruation. (x) Non-injury bleeding from the surface of the skin, mouth or any other opening of the body.
Genetic disorders • The genetic disorders like Down’s syndrome, Edward’s syndrome, Patau’s syndrome, Cri-du-chat syndrome, Turner’s syndrome, Klinefelter’s syndrome, Superfemales, Supermales, Alkaptonuria, Phenylketonuria, Albinism, TaySach’s disease, Gaucher’s disease, Sickle cell anaemia, Thalassaemias, Alzheimer’s disease, Haemophilias, Redgreen colour blindness, Night blindness and Muscular dystrophy are also non-communicable diseases.
Multiple Choice Questions 1. Which of the following causes plague? (a) Trichinella spiralis (b) Salmonella typhimurium (c) Yersinia pestis (d) Leishmania donovani. 2. Typhoid fever is caused by (a) Shigella (b) Escherichia (c) Giardia (d) Salmonella. 3. The disease, in which thick cough stops the passage of throat and form a layer of mucous membrane, is called (a) tuberculosis (b) tetanus (c) diphtheria (d) pertussis. 4. Which of the following is also known as Biowar disease? (a) Plague (b) Anthrax (c) Malaria (d) Giardiasis. 5. Malignant tertian malaria is caused by (a) Plasmodium vivax (b) Plasmodium ovale (c) Plasmodium falciparum (d) Plasmodium malariae. 6. In malaria, which of the following is released in blood to
cause chills and fever? (a) Hematin (b) Haemozoin (c) Schuffner’s dots (d) Hematocrin. 7. The infective stage of Entamoeba histolytica is (a) spore (b) egg (c) trophozoite (d) cyst. 8. Leishmania tropica causes (a) sleeping sickness (b) kala-azar (c) oriental sores (d) none of these. 9. ‘Lock jaw’ is another name of (a) malaria (b) kala-azar (c) tetanus (d) diphtheria. 10. Sleeping sickness is caused by (a) Wuchereria bancrofti (b) Trypanosoma gambiense (c) Plasmodium (d) Varicella zoster. 11. Amoebiasis in human is acquired through (a) viral infection (b) contamination of food with cysts
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(c) accidental consumption of amoebic trophozoites. (d) none of the above 12. Which of these sets is incorrect? (a) Plasmodium falciparum, malaria, relapse, mosquito (b) Trypanosoma gambiense, Glossina, sleeping sickness, wool sorter’s disease (c) Clostridium tetani, tenanospasmin, DPT (d) Entamoeba histolytica, dysentery, quadrinucleate cyst, colon. 13. ORS is needed in which of the following diseases? (a) Cholera (b) Diphtheria (c) Tuberculosis (d) Whooping cough. 14. Hyaluronidase is secreted by (a) Giardia intestinalis (b) Trypanosoma gambiense (c) Balantidium coli (d) Yersinia pestis. 15. The infectious stage of Plasmodium is (a) sporozoite (b) cryptozoite (c) trophozoite (d) metacryptozoite. 16. ‘Bubonic plague’ is transmitted by (a) rat flea (b) mosquito (c) cockroach (d) house fly. 17. Chaga’s disease is caused by (a) Trypanosoma gambiense (b) T. cruzi (c) Leishmania donovani (d) T. rhodesiensi. 18. Adults of Wuchereria bancrofti attack (a) excretory system (b) nervous system (c) blood circulation (d) lymph vessels. 19. In rheumatoid arthritis, (a) there is accumulation of uric acid crystals in synovial joints (b) there is an inflammation of the synovial membrane (c) only the cartilage at synovial joints is affected (d) all of the above. 20. Poor person’s disease is (a) CVA (b) MI (c) RHD (d) RA. 21. Insulin dependent diabetes mellitus is caused by (a) failure of b-cells to produce adequate amount of insulin (b) failure of a-cells to produce adequate amount of insulin (c) failure of insulin to facilitate the movement of glucose into cells. (d) failure of insulin to facilitate the movement of glycogen into cells. 22. Which of the following match is correct? (a) Tinea pedis – Ringworm of nose (b) Tinea capitis – Ringworm of scalp (c) Tinea cruris – Ringworm of neck (d) Tinea barbae – Ringworm of groin. 23. The primary host for Taenia solium is (a) dog (b) pig (c) cat (d) human being. 60
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24. What is the common name of Trichuris trichuria? (a) Hook worm (b) Whip worm (c) Pin worm (d) Seat worm. 25. Cysticercosis is caused by (a) Taenia solium (b) larva of T.solium (c) Echinococcus (d) Ascaris. 26. Which one of the following options gives the correct matching of a disease with its causative organism and mode of infection? Disease Causative Mode of organism infection (a) typhoid Salmonella with inspired air typhi (b) pneumonia Streptococcus droplet infection pneumoniae (c) elephantiasis Wuchereria with infected bancrofti water and food (d) malaria Plasmodium bite of male vivax Anopheles mosquito 27. Hodgkin’s disease is an example of (a) osteoma (b) carcinoma (c) leukemia (d) lymphoma 28. Match the causative organisms with their diseases. (A) Haemophilus influenzae (1) Malignant malaria (B) Entamoeba histolytica (2) Elephantiasis (C) Plasmodium falciparum (3) Pneumonia (D) Wuchereria bancrofti (4) Typhoid (E) Salmonella typhi (5) Amoebiasis (a) A – 1, B – 5, C – 3, D – 2, E – 4 (b) A – 3, B – 5, C – 1, D – 2, E – 4 (c) A – 5, B –1, C – 3, D – 4, E – 2 (d) A – 1, B – 3, C – 2, D – 5, E – 4 29 Which of the following is not a character of cancerous tissues in our body? (a) Contact inhibition (b) Neoplasia (c) Metastasis (d) Inability for differentiatio 30. Which one of the following is a correct match ? (a) Filariasis – Taenia solium (b) Encephalitis – Culex vishnui (c) Malaria – Phlebotomus sp. (d) Kala-azar – Anopheles stephensi
answer key 1. 6. 11. 16. 21. 26.
(c) (b) (b) (a) (a) (b)
2. 7. 12. 17. 22. 27.
(d) (d) (b) (b) (b) (d)
3. 8. 13. 18. 23. 28.
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(c) (c) (a) (d) (d) (b)
4. 9. 14. 19. 24. 29.
(b) (c) (c) (b) (b) (a)
5. 10. 15. 20. 25. 30.
(c) (b) (a) (c) (b) (b) nn
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1. Identify X, Y and Z in the given equation of photosynthesis X + 12H2O Y + Z + 6O2 X Y Z (a) 6CO2 C6H12O6 6H2O (b) 2H2A 2A O2 (c) CH2O C6H12O6 6CO2 (d) CO2 C6H12O6 12H2O. 2. T.W. Engelmann experiment of photosynthesis involved (a) Cladophora and anaerobic bacteria. (b) Blue green algae and purple sulphur bacteria. (c) Cladophora and oxygen scavenging bacteria. (d) Green algae and green sulphur bacteria. 3. Which of the following can be referred as “Hill reagent” in plants? (a) ATP (b) NADP+ (c) NADPH+ (d) FADH2. 4. The anaerobic photoautotrophic green sulphur and purple sulphur bacteria use (i) as a source of electrons in photosynthesis and produce (ii) as a by product. (i) (ii) (a) H2S, Sulphur (b) H2O Oxygen (c) Sulphur H2S (d) Oxygen H2O. 5. Which of the following statements is/are not true regarding T.W. Engelmann photosynthesis experiment? (i) Aerobic bacteria were used to detect the sites of O2 evolution. (ii) Bacteria were accumulated only in the region of blue light. (iii) Purple and green bacteria were used as oxygen scavengers. (iv) Light splitted into its spectral component were used to illuminate the green algae.
6.
(a) (i), (iii) and (iv) (b) (ii) and (iv) (c) only (iii) (d) (ii) and (iii). Refer the given statements. (i) Photosynthesis occurs only in the green leaves of plants. (ii) Membranous system of chloroplast is responsible for the synthesis of ATP and NADPH. (iii) Dark reactions are not light dependent reactions. (iv) Dark reactions depend on ATP and NADPH. Which of the given statements is/are true regarding photosynthesis? (a) (i), (iii) and (iv) (b) (ii) and (iv) (c) only (iv) (d) (i), (ii) and (iv). 7. Given below are the graphs showing the absorption spectra of photosynthetic pigments, out of which one is showing the action spectrum of photosynthesis.
Identify the photosynthetic pigments for the given graphs and identify the graph showing action spectrum. A B C D (a) Chlorophyll a Carotenoids Action Chlorophyll b spectrum (b) Chlorophyll a Action Carote- Chlorophyll b spectrum noids (c) Chlorophyll b Carotenoids Chloro- Action phyll a spectrum (d) Carotenoids Chlorophyll b Action Chlorophyll a spectrum 8. The most abundant plant pigment in the world is (a) Carotenoid (b) Xanthophylls (c) Chlorophyll (d) All of these.
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9. Carotenoids and Xanthophylls are (i) . They absorb light and transfer the energy to (ii) and also protect it from (iii) . (i) (ii) (iii) (a) Accessory Chlorophyll - a Photooxidation pigments (b) Respiratory Chlorophyll - b Photoreduction pigments (c) Accessory Chlorophyll - a Phototaxis pigments (d) Respiratory Chlorophyll - a Photooxidation pigments. 10.
Match Column - I and Column - II on the basis of given graph and select the correct option. Column - I Column - II (i) Limiting factor in (a) Some factor other than region P light intensity is becoming the limiting factor (ii) Q represents (b) Light is no longer limiting factor (iii) R represents (c) Light intensity (iv) S represents (d) Maximum rate of photosynthesis (v) T represents to (e) Saturation point for light intensity. (a) (i) - (a), (ii) - (b), (iii) - (c), (iv) - (d), (v) - (e) (b) (i) - (c), (ii) - (a), (iii) - (b), (iv) - (e), (v) - (d) (c) (i) - (d), (ii) - (b), (iii) - (e), (iv) - (c), (v) - (a) (d) (i) - (e), (ii) - (d), (iii) - (c), (iv) - (b), (v) - (a). 11. Identify A, B, C, D and E in the Z scheme of light reaction.
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B
C
D
E
H+ e– acceptor acceptor
(b) Photo system-I
e– e– PhotoNADPH2 acceptor transport system II + ATP system
(c)
e– e– PhotoNADP+ acceptor transport system II system
Photo system-I
(d) Photo system-II
P680
e– e– Photoacceptor transport system I system
NADP+
NADPH + H+
12. Electrons in the reaction centre of PS-I excited as they receive red light of wavelength 700 and transfer to another acceptor molecule which have (a) greater redox potential (b) lower redox potential (c) equal redox potential (d) no redox potential. 13. Refer the given diagram of a section of chloroplast.
Identify X, Y, Z and their respective function. X
Y
Z
Structure
Function
Structure
Function
Structure
Function
(a)
Grana
Light absorption
Starch Granule
Carbohydrate storage
Stroma
CO2 fixation
(b)
Grana
Photolysis of water
Stroma
CO2 fixation
Starch granule
Carbo hydrate storage
(c)
Stroma
Photolysis of water
Grana
CO2 fixation
Starch granule
Carbo hydrate storage
(d)
Stroma
CO2 fixation
Grana
Photolysis of water
Starch granule
Carbo hydrate storage
14. In the process of photosynthesis splitting of water is associated with (a) photosystem I (b) chlorophyll b (c) photosystem II (d) xanthophylls.
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A
(a) P 700
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15. The electron needed to replace those removed from photosystem I are provided by (a) C3-cycle (b) PS II (c) ATP (d) splitting of H2O. 16. Match column - A with column - B and select the correct option from the codes given below. Column - A Column - B (A) RuBisCO (i) Accessory pigment (B) PEPCase (ii) Absorption maxima at 700 nm (C) PS II (iii) C3 - cycle (D) Carotenoids (iv) Absorption maxima at 680 nm (E) PS I (v) C4 cycle (a) A - (ii), B - (iv), C - (i), D - (iii), E - (v) (b) A - (v), B - (i), C - (iv), D - (ii), E - (iii) (c) A - (iii), B - (i), C - (ii), D - (v), E - (iv) (d) A - (iii), B - (v), C - (iv), D - (i), E - (ii). 17. When PS I is excited with the light of wavelengths beyond 680 nm, phosphorylation occurs due to cyclic flow of electrons, results in synthesis of (a) NADPH + H+ and ATP (b) only NADPH + H+ (c) only ATP (d) NADPH and ADP. 18. Refer the given flow chart of light reaction and identify A, B and C.
A B C (a) PS I e– acceptor Chlorophyll P700 (b) PS II e–acceptor Chlorophyll P680 (c) PS I e–acceptor Chlorophyll P680 (d) PS II Chlorophyll P700 LHC. 19. Which of the following process/es is/are responsible for the development of proton gradient across the membrane of thylakoid? (i) Splitting of water molecules to the inner side of the membrane of the thylakoid. (ii) Movement of electrons through the photosystem. (iii) Splitting of water molecule at the stroma side. (iv) Removal of protons from the stroma by NADP reductase. (v) Removal of NADPH + H+ from the lumen.
(a) (i), (ii) and (v) (b) (i), (ii) and (iv) (c) only (i) (d) (i), (ii), (iv) and (v). 20. Given below is the pathway of ATP synthesis through chemiosmosis.
Identify A, B, C, D and E. A B C D E (a) PS I PS II F1 Lumen F0 (b) F0 F1 PS I PS II Lumen (c) F0 PS II PS I Lumen F1 (d) Lumen PS I PS II F0 F1. 21. Synthesis of ATP by chemiosmosis requires (a) ATPase (b) proton pump (c) proton gradient (d) all of these 22. Refer the given flowchart of biosynthetic phase and identify A, B and C.
A B (a) 3 PGA RuBP (b) RuBP 3PGA (c) Triose RuBP (d) RuBP Triose phosphate
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23. First stable product of CO2 fixation in C4 plant is (a) OAA (b) 3 PGA (c) RuBP (d) pyruvate. 24. After world war - II, to discover the first CO2 fixation product Melvin Calvin use radioactive carbon (a) 18C (b) 14C 16 (c) C (d) none of these. 25. The enzyme RuBisCO is a/an (a) carboxylase (b) oxygenase (c) dehydrogenase (d) both (a) and (b). 26. Number of turns of C3 cycle required to synthesize one molecule of glucose from the pathway is (a) 12 (b) 2 (c) 6 (d) 3. 27. Energy required to synthesize one molecule of glucose through the Calvin pathway is (a) 3 ATP and 2 NADPH (b) 18 ATP and 12 NADPH (c) 12 ATP and 18 NADPH (d) 2 ATP and 3 NADPH. 28. Which of the following statement is not true regarding RuBisCO? (i) It has both carboxylase as well as oxygenase activity. (ii) It is the most abundant of all natural proteins. (iii) It is abundant in mesophyll cells. (iv) It has greater affinity for O2. (v) It has ribulose bisphosphate as substrate. (a) (iii) and (iv) (b) (ii) and (iv) (c) only (ii) (d) (i), (ii) and (v). 29. Plants adapted to dry tropical regions show (a) C4 pathway (b) C3 pathway (c) both (a) and (b) (d) photorespiration 30. Which of the following is a C4 plant? (a) Rice (b) Soyabean (c) Wheat (d) Sugarcane. 31. C4 plants are special because (a) they tolerate higher temperatures (b) they show a response to high light intensities (c) they lack photorespiration and have greater productivity (d) all of these 32. During the carbon dioxide fixation, first stable compound formed in C4 plant contains ______. (a) 2C (b) 5C (c) 4C (d) 3C. 33. The primary CO2 acceptor for CO2 fixation, in C4 plants is (a) 3C molecule (b) 4C molecule (c) 2C molecule (d) 6C molecule. 34. Refer the given cycle of CO2 fixation and identify A, B, C, D and E. 64
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A (a) Bundle
B
C
D
E
Mesophyll OAA Decarbo- Regenera sheath cell cell xylation tion (b) Mesophyll Bundle OAA Decarboxy- Regenera cell sheath lation tion cell (c) Mesophyll Bundle 3PGA Regenera- Decarboxy cell sheath tion lation cell (d) Bundle Mesophyll 3PGA Regenera- Decarboxy sheath cell tion lation cell 35. During the CO2 fixation in C4 plants, CO2 released from 4-carbon compound and enters into Calvin pathway, this process takes place in (a) bundle sheath cell (b) vascular tissues (b) mesophyll cell (d) mitochondria. 36. Which of the following plants shows Kranz anatomy? (a) Wheat (b) Maize (c) Sugarcane (d) Both (b) and (c).
37. The bundle sheath cells of a C4 plant are (a) rich in PEPcase but lack RuBisCO (b) rich in RuBisCO and PEPcase (c) rich in RuBisCO but lack PEPcase (d) do not participate in CO2 fixation. 38. C4 plants show high productivity and yields because (a) they are succulent (b) they lack photo-respiration (c) they have Kranz anatomy (d) they have PEP carboxylase.
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39. Which of the following statements is/are correct regarding to C4 plant? (i) Calvin cycle takes place in mesophyll cells. (ii) PEP is the primary CO2 acceptor molecule. (iii) High CO2 fixation rate under high light intensity. (iv) Have high rate of photorespiration (v) Can be identify by Kranz anatomy. (a) (i) and (iv) (b) (i), (ii), (iii) and (v) (c) (iii) and (v) (d) only (i). 40. Law of limiting factors was given by (a) T.W. Engelmann (b) Blackman (c) Cornelius Van Niel (d) Joseph Priestley. 41. The mechanisms of ATP formation both in chloroplast and mitochondria is explained by (a) relay pump theory of Godlewski (b) cholodny Went’s hypothesis (c) chemiosmotic hypothesis (d) munch’s pressure/mass flow model. 42. If photosynthesizing green algae (oxygenic photosynthesis) are provided with CO2 labelled with an isotope of oxygen (18O that is “heavy” but not radioactive), later analysis will show that all of the following compounds produced by the algae contain the 18O label except (a) PGA (b) RuBP (c) glucose (d) O2. 43. In Calvin cycle which stage needs ATP? (a) Carboxylation only (b) Only regeneration (c) Both carboxylation and reduction (d) Both reduction and regeneration. 44. The diagram shows the movement of substances into in and out of a chloroplast.
What do labels 1 to 4 represent? 1 2 3 4 (a) CO2 ATP H2O Starch (b) CO2 H2O Sugars O2 (c) H2O O2 CO2 Sugar (d) Sugar H2O ATP O 2. 45. The below diagram is the cyclic series of reactions that occurs during carbon fixation stage of photosynthesis.
Carbon dioxide is taken into the cycle at stage A . Hydrogen from reduced hydrogen acceptor is used at stage B . Energy from ATP is used to drive stage C . The substance formed at position Y is D . If one molecule of substance Y is released per cycle, how many E times must the cycle turn for one molecule of sucrose (C12H22O11) to be built up at position Z ? (a) A - 4; B - 2; C - 2 and 3; D - 3 -carbon sugar; E - 4. (b) A - 3; B - 3; C - 1 and 2; D - pyruvate acid, E - 2. (c) A - 2; B - 4; C - 3 and 4; D - glucose-1-phosphate, E - 8. (d) A - 1; B - 1; C - 2 and 4, D - citric acid; E - 12. 46. DCMU also called ‘DIURON’ is a potent non selective herbicide it kills plant by (a) inhibiting light reaction-I (b) inhibiting light reaction-II (c) inhibiting Calvin cycle (d) inhibiting Krebs’ cycle. 47. What is the effect of high CO2 concentration and higher values of ATP/ADP ratio? (a) Rate of Calvin cycle is increased (b) Rate of Kreb’s cycle is decreased (c) Rate of Calvin cycle is decreased and Krebs’ cycle is increased (d) Rate of Calvin cycle is increased and that of Krebs’ cycle and Glycolate cycle is decreased. 48. Two groups of isolated thylakoids are placed in an acidic bathing solution so that H+ diffuses into the thylakoids. They are then transferred to a basic bathing solution, and one group is placed in the light, while the other group is kept in the dark. Select the option that describes expected production in each group of thylakoids. In Light In Dark (a) ATP only Nothing (b) ATP, O2 ATP only (c) ATP, O2, glucose ATP, O2 (d) ATP, O2 O2. 49. CAM helps the plants in (a) reproduction (b) conserving water (c) secondary growth (d) disease resistance.
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50. The possible advantages of absence of grana in the chloroplasts of bundle sheath cells of C4 leaves is (a) division of labour (b) more formation of malic acid (c) no competition between oxygen and carbon dioxide for active sites of enzyme RuBisCo (d) occurrence of excessive photolysis of water. 51. During fixation of one molecule of CO2 by C3 plants, number of ATP and NADPH2 required are (a) 3 ATP and 2 NADPH2 (b) 5 ATP and 2 NADPH2 (c) 3 ATP and 6 NADPH2 (d) 18 ATP and 12 NADPH2 52. A process that makes important difference between C3 and C4 plants is (a) transpiration (b) glycolysis (c) photosynthesis (d) photorespiration. 53. Emerson’s effect indicates the existence of (a) two pigment systems (b) two photosynthetic units (c) two photophosphorylations (d) none of the above. 54. In which wavelength of light photosynthesis is maximum? (a) Red light (b) Green light (c) Violet light (d) Ultra-violet light. 55. Chlorophyll consists of (a) a head of phytol and tail of four pyrrole rings (b) a head of linked carbons and tail of four pyrrole rings (c) a head of four pyrrole rings and tail of linked nitrogens (d) a head of four pyrrole rings and an alcoholic phytol tail. 56. In CAM plants, the end product of dark fixation which is stored inside the vacuoles is (a) starch (b) oxaloacetic acid (c) sugar (d) malic acid. 57. The correct molecular formula of chlorophyll a is (a) C55H70O5N4Mg (b) C55H72O6N4Mg (c) C55H70O6N4Mg (d) C55H72O5N4Mg. 58. Photorespiration is favoured by (a) high temperature and low O2 (b) high humidity and temperature (c) high O2 and low CO2 (d) high CO2 and low O2. 59. Which pigment system is inactivated in red drop? (a) PS I and PS II (b) PS I (c) PS II (d) None of these. 60. Stomata of CAM plants (a) are always open (b) open during the day and close during the night (c) open during the night and close during the day (d) never open. 66
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61. Photosynthetically active radiation (PAR) represents the following range of wavelength (a) 500-600 nm (b) 450-950 nm (c) 340-450 nm (d) 400-700 nm. 62. In C3 plants, first stable product of photosynthesis during dark reaction is (a) PGA (b) PGAL (c) RuBP (d) OAA. 63. The factor, which is not limiting in normal conditions for photosynthesis, is (a) water in plant cell (b) sunlight (c) chlorophyll content of leaf (d) carbon dioxide. 64. A decrease in photosynthetic rate with increased availability of oxygen is called (a) Richmond Lang effect (b) Warburg effect (c) Blackman’s law of limiting factors (d) Emerson’s enhancement effect. 65. Match the phenomenon listed under column I with their descriptions given in column II and select the correct answer from the codes given below. Column I Column II A Warburg effect p Change in gene frequency by chance B Pasteur effect q Postponing senescence in the leaves by applying cytokinin C Emerson effect r Decline in the consumption of respiratory substrate due to a change from anaerobic to aerobic respiration D Wright effect s Inhibitory effect of O2 on photosynthesis t Enhancement of photosynthesis by subjecting chlorophyll to two different wavelengths of light. (a) A = s, B = t, C = q, D = r (b) A = t, B = r, C = p, D = s (c) A = t, B = s, C = p, D = q (d) A = s, B = r, C = t, D = p. 66. In an experiment demonstrating the evolution of oxygen in Hydrilla, sodium bicarbonate is added to water in the experimental set-up. What would happen if all other conditions are favourable? (a) Amount of oxygen evolved decreases as the availability of carbon dioxide increases. (b) Amount of oxygen evolved increases as carbon dioxide in water is absorbed by sodium bicarbonate. (c) Amount of oxygen evolved decreases as carbon dioxide in water is absorbed by sodium bicarbonate. (d) Amount of oxygen evolved increases as the availability of carbon dioxide increases.
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67. Bacteria that uses chemical energy to fix CO2 are known as (a) chemoautotroph (b) photoautotroph (c) heterotroph (d) none of these. 68. Which of the following is wrongly matched? (a) Sorghum – Kranz anatomy (b) Blackman – law of limiting factors (c) Photorespiration – C3 plants (d) PS II – P700. 69. Th e c o n v e r s i o n o f p h o s p h o g l y c e r i c a c i d t o phosphoglyceraldehyde during photosynthesis can be described as (a) oxidation (b) hydrolysis (c) electrolysis (d) reduction. 70. Sunken stomata are usually found in (a) C3 plants (b) CAM plants (c) insectivorous plants (d) phanerogams. 71. Photo-oxidation of water results in the formation of (a) H+, O2 and ATP (b) H+, O2, e– and ATP + – (c) H , O2 and e (d) none of these. 72. Which of the following pigments is water soluble? (a) Chlorophyll (b) Xanthophyll (c) Phycobilin (d) Carotenoids. 73. Photosystem II located in in (a) grana (b) entire chloroplast (c) stroma (d) chloroplast membrane. 74. Source of CO2 for photosynthesis during day in CAM plants is (a) 3-PGA (b) malic acid (c) oxalo-acetic acid (d) pyruvate. 75. The first reaction in photorespiration is (a) carboxylation (b) oxygenation (c) decarboxylation (d) phosphorylation. 76. In photosynthetic electron transport system, manganese ions are associated with (a) oxygen evolving complex (b) CF0 – CF1 complex (c) cytochrome b6–f complex (d) plastoquinone. 77. In which of the following the rate of transpiration is high? (a) CAM plants (b) C3 plants (c) C3 and C4 plants (d) C4 plants. 78. Which of the following statements is/are incorrect regarding photorespiration? (i) In this process RuBP binds with O2 and is converted into one molecule of phosphoglycerate and phosphoglycolate. (ii) In this process RuBP binds with O2 and is converted into 2 molecules of phosphoglycolate. (iii) In photorespiratory pathway, there is neither synthesis
of sugars, nor of ATP. (iv) This pathway results in the release of CO2 with the utilization of ATP. (a) (i) & (ii) (b) (ii) only (c) (ii) & (iii) (d) (ii) & (iv). 79. Cornelius van Niel, based on his studies of purple and green bacteria, demonstrated that photosynthesis is essential a light dependent reaction in which hydrogen from a suitable oxidizable compound reduces carbon dioxide to carbohydrates. This can be expressed by
(a) CO2 + H2O
[CH2O] + O2
(b) 2H2A + CO2
2A + [CH2O] + H2O
(c) 2H2S + 2CO2
2H2SO4 + 2C
(d) C6H12O6 + 6O2 +6H2O 6CO2 + 12H2O. 80. The graph shows the oxygen released and taken up by a tree during a 24 hour period.
Which statement describes the situation at point X? (a) Respiration begins (b) Photosynthesis stops (c) The rate of respiration is equal to the rate of photosynthesis (d) The rate of respiration is greater than the rate of photosynthesis. 81. To generate one molecule of NADPH, ________ photons must be absorbed : ________ from photosystem I and _________ from photosystem II. Select the correct sequence of words to complete the above paragraph. (a) Four, two, two (b) Two, one, one (c) three, two, one (d) Four, three, one 82. In an experiment, the carbon dioxide available to a C3 plant was labelled with a radioactive isotope and the amount of radioactivity in the chloroplast was measured. As photosynthesis proceeded, in which of the following molecules did the radioactivity first appear? (a) PGAL (b) PEP (c) PGA (d) RuBP 83. In an experiment, the carbon dioxide available to a C4 plant was labelled with a radioactive isotope, and the
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amount of radioactivity in the chloroplast was measured. As photosynthesis proceeded, in which of the following molecules did the radioactivity first appear? (a) Oxaloacetic acid (b) PEP (c) Malic acid (d) RubP 84. The minerals involved in water-splitting reaction during photosynthesis are (a) magnesium and chlorine (b) potassium and manganese (c) manganese and chlorine (d) molybdenum and manganese 85. During Calvin cycle, which enzyme is used to convert xylulose 5 phosphate to ribulose-5-phosphate? (a) Transketolase (b) Isomerase (c) Epimerase (d) Phosphotase 86. Which one of the following would be least limiting for photosynthesis? (a) Oxygen (b) Light (c) Carbon dioxide (d) Temperature 87. Match column I with column Ii and select the correct codes given below. Column I Column II (A) Oxygen evolving (i) ATP synthesis complex (B) Proton gradient (ii) High oxygen concentration (C) Photorespiration (iii) Kranz anatomy (D) C4 plants (iv) Photolysis of water (a) A-(ii), B-(iv), C-(iii), D-(i) (b) A-(iv), B-(i), C-(ii), D-(iii) (c) A-(iv), B-(i), C-(ii), D-(iii) (d) A-(ii), B-(i), C-(iv), D-(iii) 88. Refer the given showing interrelationship of two phases of photosynthesis. Name the product labelled as A, B and C.
(a) A–NADP+, B–PEP, C-Carbohydrate (b) A–NADPH, B–PEP, C-Malic acid (c) A–NADP+, B–RiBP, C–OAA (d) A–NADPH, B–ATP, C–Carbohydrate 89. Photorespiration is the catabolism of _______, forms _______ and _______ with the synthesis of _______ molecules of ATP. Select the correct sequence of words to complete the above paragraph. (a) PGAL, PGA, CO2, Zero (b) RuBP, PGA, CO2, Zero (c) RuBP, CO2, OAA, Zero (d) PGA, RuBP, CO2, Six 90. Which of the following comparisons is incorrect? C3 plants
C4 plants
(a) Rate of photosynthesis is quite high
Rate of photosynthesis is negligible
(b) Mesophyll cells perform complete photosynthesis
Mesophyll cells perform only initial fixation
(c) Optimum temperature is 30-45°C
Optimum temperature for photosynthesis is 10-25°C
(d) The leaves do not The leaves have kranz possess kranz anatomy anatomy Answer key 1. 6. 11. 16. 21. 26. 31. 36. 41. 46. 51. 56. 61. 66. 71. 76. 81. 86.
(a) (b) (d) (d) (d) (c) (d) (d) (c) (b) (a) (d) (d) (d) (c) (a) (a) (a)
2. 7. 12. 17. 22. 27. 32. 37. 42. 47. 52. 57. 62. 67. 72. 77. 82. 87.
(c) (b) (a) (c) (b) (b) (c) (c) (d) (d) (d) (d) (a) (a) (c) (b) (c) (c)
3. 8. 13. 18. 23. 28. 33. 38. 43. 48. 53. 58. 63. 68. 73. 78. 83. 88.
(b) (c) (b) (a) (a) (a) (a) (b) (d) (b) (a) (c) (c) (d) (a) (b) (a) (d)
4. 9. 14. 19. 24. 29. 34. 39. 44. 49. 54. 59. 64. 69. 74. 79. 84. 89.
(a) (a) (c) (b) (b) (c) (b) (b) (c) (b) (a) (c) (b) (d) (b) (b) (c) (b)
5. 10. 15. 20. 25. 30. 35. 40. 45. 50. 55. 60. 65. 70. 75. 80. 85. 90.
(d) (b) (b) (c) (d) (d) (a) (b) (a) (c) (d) (c) (d) (b) (b) (c) (c) (c) nn
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By : Sheetal Srivastava
• Population dispersal may bring change in the size of population by causing the propagation of the individuals
into and out of an area. Thus it is responsible for wider distribution of individuals, protection from overcrowding, predators, etc.
• Population Density is influenced by Natality (B), Mortality (D), Immigration (I) and Emigration (E). If N is the population density at time t, then its density at time t + 1 is
Nt + 1 = Nt + [ (B + I) – (D + E)]
Thus, population density will increase if, (B + I) > (D + E) and population density will decrease if, (B + I) < (D + E)
For exam analysis refer ‘Quick PMT Revision’ of December’ 12 issue
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WorldMags.net Table: Showing features of two basic patterns of population growth forms Feature
S-shaped growth form
J-shaped growth form
1.
Growth curve
Sigmoid/logistic or Verhulst. Pearl Logistic
2.
Occurrence
Most organisms including human being Few organisms including reindeer, algal blooms, annual plants
3.
Population type
Stable
Erruptive
4.
Equilibrium
Attained while population size approaches carrying capacity.
Never attained
5.
Number of phases
Five - lag, positive acceleration, exponential, negative acceleration and stationary phase
Two - lag and exponential phase
6.
Environmental resistance to slow down exponential phase
Operates
Does not operate
7.
Crash phases
Does not occur
Occurs at the end of growth
8.
Equation
dN K −N = rN K dt
dN = rN dt
9.
Graph
Exponential
• The ratio of various age groups in a population determines the current reproductive status of the population and also indicates what may be expected in the future.
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• The process of preventing growth of other organisms through secretion of toxic chemicals is called allelopathy. • Smoother crops do not allow weeds to grow, e.g., sorghum, sunflower, barley. Sacred basil (Ocimum sanctum, vern tulsi) does not allow other plants to flourish nearby. Convolvulus arvensis inhibits germination of wheat seeds. Trichoderma checks growth of Aspergillus, Chlorella in case of diatom Nitzschia frustrulum, Tagetes kills soil nematodes while walnut (Juglans nigra) produces allochemic juglone for preventing growth of apple, tomato, alfalfa, etc.
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Some points to remember
• Ecosystem is the self-sufficient unit comprising a biotic community and its abiotic physico-chemical environment. Ecosystem many be natural or artificial. • Ecological niche is the specific place where species plays its role (functions). In other words, it means species functional position in an ecosystem. • Climatic factors include temperature, light, air, water, atmospheric humidity, rain etc. while edaphic factors include factors of soil e.g., soil texture, substratum, topography, background, minerals and pH. • Population growth is determined by interaction of 3 factors: biotic potential, environmental resistance and carrying capacity of environment. Biotic potential is the natural capacity of organisms to produce offspring. Environmental resistance refers to the factors that do not allow all offspring to survive. Carrying capacity is the limit to population size that environment can support. • Community induces population of different species that live together in the same habit and interact through trophic and spatial relationship to form a self-sustained unit. • The short-term properties of the atmosphere such as temperature humidity, rainfall, pressure, sunshine, wind etc. at a given place and time is called weather. • Climate refers to the average weather conditions of a particular area. Climate also includes general patterns of atmospheric conditions, seasonal variations and weather extreme averages over long periods. • Plants show strategic adaptations to light regimes and are accordingly termed as sun plants (heliophytes) or shade plants (sciophytes).
• Plants adapted to saline environments are termed halophytes. These reveal special modifications to obtain oxygen and living in salty conditions. • Plants adapted to oligotrophic soils generally possess mycorrhizae (mutualistic association of plant roots with fungi).
• Ectotherms are cold blooded animals having body temperature matching with the environmental temperature. They are affected by temperature variations • Endotherms are warm blooded animals which can regulate their body temperature by physiological means and maintain more or less constant internal temperature. • A natural association of the interdependent populations of different species inhabiting a common environment or habitat as a viable, self-contained unit is called a biotic community. • Keystone species include few animals that produce longlasting changes which alter or maintain their environment. Critical link species play important role in supporting network species by providing food or acting as pollinators or dispersal agents etc. • Ecotones are the transition zones between two adjoining communities. They have rich species diversity as compared to adjoining communities and this phenomenon is called edge effect. • Gause hypothesis or principle of competitive exclusion states that an ecological niche cannot be simultaneously and completely occupied by established populations of more than one species. One of the two species is eliminated. nn
Question : Plants grow with sunlight and why not with tube light?
– Sunil. R. Hanam Shetty; Karnataka
Answer : Yes, plants can show growth in tube light. Photosynthesis is a physico-chemical process by which plants use light energy to drive the synthesis of organic compounds, required for the growth of a plant. Plants need light, CO2, chlorophyll and water as raw materials to perform photosynthesis. In this case, we are considering tube light instead of sun light. When we use tube light, its intensity will be lower than the sunlight but under lower light intensity, photosynthesis can take place. Thus, a plant can grow under tube light but at low rate. 72
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and used in overcoming entropy as well as for performing various body activities. Hence, pyramid of energy is always upright and can never be inverted.
1. Differentiate between autotomy and regeneration. Ans. Autotomy (Self amputation): It is the breaking off the injured or unduly stimulated body parts. In this method
injured parts are get ridden by the replacement with the perfect ones. Process of autotomy is fast.
Regeneration : It is a process by which the replacement of lost parts occurs. It occurs after the autotomy process. Process of regeneration is slow. It may take even 1 year. E.g., Echinoderms have great power of autotomy and regeneration.
2. Embryo culture has emerged as a significant technique for producing rare interspecific and intergeneric hybrids. Discuss. Ans. Embryo culture is the technique of taking out young embryos from developing seed and growing them on culture medium to form seedling and then young plants. In intergeneric and interspecific hybrids, embryo abort at earlier or later stages. By using embryo culture, we can save rare hybrids. In this technique, embryo is excised at younger stage and is cultured in culture medium. In this way, embryo culture has emerged as a significant technique for producing rare interspecific and intergeneric hybrids. 3. Meiosis I produces haploid daughter cells. Which of its subphases carries out reduction in chromosome number? Elaborate. Ans. Meiosis I consists of four subphases. Out of the four,
anaphase-I carries out the reduction in chromosome number. In anaphase-I, from each tetrad, two chromatids of a chromosome move as a unit (dyad) to one pole of a spindle, and the remaining two chromatids move to the opposite pole separating homologous chromosomes of each pair. Hence, half of the chromosomes, go to each pole. 4. Interfascicular cambium is secondary meristem while intrafascicular cambium is primary. Explain. Ans. Interfascicular cambium arises secondarily by the meristematic activities of some cells of medullary rays. Thus, it is secondary cambium while, intrafascicular cambium occurs as strips in between primary xylem and primary phloem. It is primary meristem. 5. ‘Pyramid of energy can never be inverted’. Justify. Ans. According to the 10% law given by Lindeman, only 10% of the total energy from a trophic level transmits to the next one. Hence the amount of energy always decreases from lower to higher trophic levels. It is dissipated as heat
6. Krebs’ cycle is a step in catabolic process of respiration, yet it is termed amphibolic pathway. Why? Ans. Krebs’ cycle provides a number of intermediates such as a-ketoglutarate and oxaloacetate which are used in different anabolic pathways to form important biomolecules like glutamate, aspartate etc. Hence the pathway is amphibolic in nature. 7. How is cri-du-chat syndrome caused? What are its symptoms? Ans. Cri-du-chat (cat cry) syndrome is caused due to deletion in the short arm of the chromosome number 5. Symptoms:
–– T he affected newborn cries like mewing of a cat. –– Affected person has a small head, widely spaced eyes, moon-like face, cry like kitten, receding chin and congenital heart disease. 8. What is the name given to the functional connecting unit between mother and foetus? What are its functions? Ans. Chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit between developing embryo (foetus) and maternal body called placenta. It acts as a barrier as well as ultrafilter between foetus and mother. It is connected to foetus by a rope-like umbilical cord which helps in the transport of substances to and from the embryo. It also acts as an endocrine tissue and produces hormones like HCG. 9. How did Francesco Redi disprove the theory of abiogenesis? Ans. Francesco Redi experimentally challenged the theory of abiogenesis. He took the flesh and cooked it so that no organisms were left alive. Then he placed flesh in 3 jars, of which, one was uncovered, the second was covered with parchment and the third one was covered with fine muslin. He kept these jars for a few days and observed that maggots developed only in the uncovered jar though the flies also visited other jars. His experiment disproved the theory of abiogenesis. 10. Define somatic hybridization. Ans. Somatic hybridization is the process of fusing protoplasts of somatic cells derived from different varieties or species of plants, on a suitable nutrients/culture medium, to produce a somatic hybrid. E.g., Pomato is a somatic hybrid between tomato and potato.
and the winner is ............. Disha XI, Hamirpur (H.P)
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NEET/PMT SPECIAL
CLASS-12
All PMT exams contain a major section of Biology MCQs. Syllabus for Biology is very vast which may make it difficult for students to cover it entirely. Keeping this in mind, a very crisp and summarized matter is presented here dealing with a unit per edition, supplemented with practice questions. It will enable students in having a quick but in-depth understanding and efficiency in practice to score excellent in NEET/PMT.
Unit-IX : BIOtechnology chapter-11 : BIOTECHNOLOGY Principles and process
•
• Biotechnology is the use of living organisms in systems
or processes for the manufacture of useful products; it may involve algae, bacteria, fungi, yeast, cells of higher plants and animals or subsystems of any of these or isolated components from living matter. • The two main techniques that gave birth to modern biotechnology are: –– Genetic engineering refers to artificial synthesis, isolation, modification, combination, addition and repair of the genetic material (DNA) by man to alter the phenotype of the host organism to suit human needs. –– Biochemical engineering involves processes that help the growth of desired microbes/eukaryotic cells in large quantities in a sterile medium (tissue culture technique) for the manufacture and multiplication of biotechnological product (antibiotics, vaccines, enzymes, medicines, hormones, etc.).
• • • • •
• The first recombinant DNA was constructed by Stanley
Cohen and Herbert Boyer in 1972. • They cut the piece of DNA from a plasmid carrying antibiotic-resistance gene in the bacterium Salmonella typhimurium and linked it to the plasmid of Escherichia coli. The vector transfers the piece of DNA attached to it. • The technique of genetic engineering includes formation of ‘recombinant DNA (rDNA)’, use of gene cloning and gene transfer.
Construction of first artificial recombinant DNA molecule • A plasmid can be used as vector to carry an alien piece of 74
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•
DNA into the host organism. The linking of antibiotic resistance gene with the plasmid vector is in the presence of the enzyme DNA ligase. DNA ligase acts on cut DNA molecules and joins the ends. This creates a combination of circular, automatically replicating DNA, called recombinant DNA. The alien piece of DNA fails to replicate until it gets integrated with the chromosomal DNA having origin of replication. This recombinant DNA is transferred into Escherichia coli, it replicate in the presence of the new host’s DNA polymerase enzyme and make multiple copies. The ability to multiply copies of antibiotic resistance gene in E. coli was termed as cloning of antibiotic resistance gene in E. coli. Three basic steps in creating genetically modified organism (GMO) or transgenic organism are: –– Identification of DNA with desirable genes. –– Introduction of the identified DNA into the host. –– Maintenance of introduced DNA in the host and transfer of the DNA to its progeny. Tools of recombinant DNA technology are –– Enzymes –– Cloning vectors (vehicle DNA) –– Competent host (for transformation with recombinant DNA).
Enzymes • Different kinds of specific enzymes are used in genetic
engineering (recombinant DNA technology). These include lysing enzymes, cleaving enzymes, synthesizing enzymes, joining enzymes and alkaline phosphatase.
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• Lysing enzymes are used to open up the cells to get
DNA for genetic experiments. Lysozyme is usually used to dissolve the bacterial cell wall.
Restriction enzymes • Restriction enzymes (cleaving enzymes) are used
to break DNA molecules. They belong to a larger class of enzymes called nucleases. • Restriction enzymes are of three types – exonucleases, endonucleases and restriction endonucleases.
• Exonucleases remove nucleotides from the terminal ends
(either 5’ or 3’) of DNA in one strand of duplex. • Endonucleases make cuts at specific position within the DNA. These enzymes do not cleave the ends and involve only one strand of the DNA duplex. • Restriction endonucleases were found by Arber in 1962 in bacteria. They act as “molecular scissors” or chemical scalpels. • They recognize the specific base sequence at palindrome sites in DNA duplex and cut its strands.
Table: Differences between exonucleases and endonucleases Exonucleases
Endonucleases
1. These nucleases cleave base pairs of DNA at their terminal They cleave DNA at any point except the terminal ends. ends. 2. They act on single strand of DNA or gaps in double stranded They cleave one strand or both strands of double stranded DNA. DNA. 3. They do not cut RNA.
They may cut RNA.
• The palindromes in DNA are base pair sequences that are the same when read forward (left to right) or backward (right to left) from a central axis of symmetry.
• Restriction endonuclease Eco R I found in the colon bacteria E.coli, recognizes the base sequence GAATTC in DNA duplex and cuts its strands between G and A as shown below:
• Three main types of restriction endonucleases are type I, and type II and type III.
• Type I restriction endonucleases require ATP, Mg2+
and S-adenosyl methionine for restriction. Type I restriction endonucleases recognise specific sites within the DNA but do not cut these sites.
• Type II restriction endonucleases are simple and require Mg2+ ions for restriction. Only type II restriction enzymes are used in recombinant DNA technology because they can be used in vitro to recognise and cut within specific DNA sequence typically consisting of 4 to 8 nucleotides and cause cleavage at unmethylated sites within their recognition.
• Type III restriction endonucleases possess both the
activities of restriction as well as methylation. Therefore, they are not used in recombinant DNA technology.
Restriction Modification System • The restriction modification system (RM System) is used by bacteria, and perhaps other prokaryotic organisms to protect themselves from foreign DNA, such as borne by bacteriophages. • Bacteria have restriction enzymes, also called restriction endonucleases, which cleave double stranded DNA at specific points into fragments, which are then degraded further by other endonucleases. This prevents infection by effectively destroying the foreign DNA introduced by an infectious agent (such as bacteriophage). • Given that the sequences that the restriction enzyme recognize are very short, the bacterium itself will almost certainly have many of these sequences present in its own DNA. Therefore, in order to prevent destruction of its own DNA by the restriction enzymes, the bacterium marks its own DNA by adding methyl groups to it. This modification must not interfere with the DNA basepairing, and therefore, usually only a few specific bases are modified on each strand.
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• The first restriction endonuclease Hin d II (hin-dee-
two) was isolated from Haemophilus influenzae. • Hin d II always cut DNA molecules at a particular point by recognising a specific sequence of six base pairs. It produces blunt ends. • The single-stranded free ends that project from each fragment of DNA duplex are known as “sticky ends”. • The sticky ends facilitate the action of the enzyme DNA ligase.
Gel electrophoresis (Separation and isolation of DNA fragments) • After the cutting of DNA by restriction enzymes, fragments •
• • •
•
of DNA are formed. These fragments can be separated by a technique called gel electrophoresis. Electrophoresis is a technique of separation of charged molecules under the influence of an electrical field so that they migrate in the direction of electrode bearing the opposite charge, through a medium/matrix. The most commonly used matrix is agarose which is a polysaccharide extracted from sea weeds. DNA fragments separate according to the size through the pores of agarose gel. The separated DNA fragments can be seen only after staining the DNA with a compound known as ethidium bromide (EtBr) followed by exposure to UV radiation as bright orange coloured bands. The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is called as elution.
Cloning Vectors • Vectors may be plasmids, a bacteriophage, cosmids, phagemids, yeast artificial chromosomes (YACs), bacterial artificial chromosomes (BACs), transposons and virus. • pBR322 vector was the first artificial cloning vector constructed in 1977 by Boliver and Rodriguez. So it is regarded as work house for gene cloning.
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Characteristics of a cloning vector • Origin of replication (Ori) : This is a sequence from
•
•
• •
where replication starts and any piece of foreign DNA can be linked to this sequence. The replication occurs inside the host cells. This new sequence is also responsible for controlling copy number of linked DNA. Selectable marker (antibiotic resistance gene) : It is also required to identify and eliminate non-transformants and selectively permit the growth of the transformants. Generally, the genes encoding resistance to antibodies such as tetracycline, ampicillin, kanamycin or chloramphenicol, etc., are useful in selectable markers for E. coli. Cloning sites : The vector must have one unique restriction site/cloning site called recognition site. Presence of a unique restriction site allows the particular enzyme to cut the vector only once. The ligation of alien DNA is carried out at a restriction site present in one of the two antibiotic resistance genes. For example, we can ligate a foreign DNA at the Bam H I site of tetracycline resistance gene in the vector pBR322. The recombinant plasmids will lose tetracycline resistance due to insertion of foreign DNA but can still be selected out from non-recombinant ones by plating the transformants on ampicillin containing medium. The transformants growing on ampicillin containing medium are then transferred on a medium containing tetracycline. The recombinants will grow in ampicillin containing medium but not on that containing tetracycline. But, non-recombinants will grow on the medium containing both the antibiotics. In this case, one antibiotic resistance gene helps in selecting the transformants, whereas the other antibiotic resistance gene gets ‘inactivated due to insertion’ of alien DNA, and helps in selection of recombinants.
Competent host • Competent host is essential for transformation with
recombinant DNA. Many kinds of host cells, including E. coli, yeast, animal and plant cells, are available for genetic engineering. Yeasts have been used extensively for functional expression of eukaryotic genes because they offer several advantages. • DNA is a hydrophilic molecule, it cannot pass through membranes, so bacterial cells must be made capable to take up DNA. This is done by treating them with a specific concentration of a divalent cation, such as calcium which increases the efficiency. • In animals, the term transformation is replaced by the term transfection. • Different alternative methods (vectorless gene transfer methods) have been used to introduce the recombinant DNA into recipient cells of animals without involving carrier molecules.
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• In a method known as micro-injection, recombinant DNA is directly injected into the nucleus of an animal cell. • In another method, suitable for plants, cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA in a method known as biolistics or gene gun.
Processes of Recombinant DNA Technology Isolation of the genetic material (DNA) • DNA is covered by the membranes which has to be break to
open the cell and to release DNA and other macromolecules like RNA, proteins, polysaccharides and lipids. It is obtained by treating the bacterial cell, plant or animal tissue with enzymes such as lysozyme (bacteria), cellulase (plant cells) and chitinase (fungus) respectively.
Cutting of DNA at specific locations • Under the optimal conditions, the purified DNA is cut by
the restriction enzyme. After the cutting of the source DNA and the vector DNA with a specific restriction enzyme, the cut out ‘gene of interest’ from the source DNA and the cut vector with space are mixed and ligase enzyme is added. This results in the preparation of a rDNA.
Amplification of gene of interest using PCR • The polymerase chain reaction or PCR, was originally
invented by Kary Mullis in 1985. PCR results in the selective amplification of a specific region of a DNA molecule and so can also be used to generate a DNA fragment for cloning. • A single PCR amplification cycle involves three basic steps:
–– Denaturation : The target DNA is heated to a high
temperature (usually 90º to 98ºC), resulting in the separation of the two strands. Each single strand of the target DNA then acts as a template for DNA synthesis. –– Annealing : The two oligo-nucleotide primers anneal (hybridize) to each of the single stranded template DNA since the sequence of the primers is complementary to the 3′ ends of the template DNA. This step is carried out at a lower temperature (usually 40º to 60ºC) depending on the length and sequence of the primers. –– Extension (Polymerisation) : Taq DNA polymerase (of a thermophilic bacterium Thermus aquaticus) synthesizes the DNA region between the primers, using DNTPs (deoxynucleoside triphosphates) and Mg2+. It means the primers are extended towards each other so that the DNA segment lying between the two primers is copied.
Applications of PCR • Some of the areas of application of PCR are mentioned here : Diagnosis of pathogen. Diagnosis of specific mutation. DNA fingerprinting. Detection of specific micro-organisms. In prenatal diagnosis. Diagnosis of plant pathogens. In palaeontology. Gene therapy.
–– –– –– –– –– –– –– ––
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Insertion of recombinant DNA into the host cell/ organism • The vector DNA (e.g., plasmid DNA) and alien (foreign) DNA
carrying gene of interest are cut by the same restriction endonuclease to produce complementary sticky ends. With the help of DNA ligase enzyme, the complementary sticky ends of the two DNAs are joined (annealing) to produce a recombinant (chimaera) DNA (rDNA). • Eukaryotic genes do not function properly when cloned into bacterial cell, because of introns. In such cases, DNA is made from mRNA by reverse transcription or synthesised artificially. • This rDNA is inserted into host bacterium by transformation using cold CaCl2 solution. The bacterial cell containing the desired rDNA is selected using selective antibiotic in the culture medium.
• The product has to be formulated with suitable preservatives.
• Such formulation has to undergo through clinical trials as in case of drugs. Strict quality control testing for each product is also required. • The downstream processing and quality control testing vary from product to product.
Obtaining the desirable gene product • When recombinant DNA is transferred into a bacterial, plant or animal cell, the foreign DNA is multiplied. The cells having cloned genes of interest can be grown on a small scale in the laboratory. The cultures may be used for extracting and purifying the desired protein.
Bioreactors (Fermenters) • Bioreactor provides the optimal conditions for obtaining the desired product by providing optimum growth conditions such as temperature, pH, substrate, vitamins, oxygen and salts. • The most commonly used bioreactors are of stirring type. A bioreactor (fermenter) has a provision for batch culture or continuous culture. In continuous culture, the culture medium is added and the product is taken out. • A stirred-tank bioreactor is usually cylindrical or with a curved base to facilitate the mixing of the reactor content. The stirrer facilitates even mixing the oxygen availability throughout the bioreactor. Alternatively air can be bubbled through the reactor. The bioreactor has an agitator system, an oxygen delivery system and foam control system, a temperature control system, pH control system and sampling ports so that small volumes of the culture can be withdrawn periodically.
Downstream processing • After completion of the biosynthetic stage, the product has to be subjected through a series of processes before it is ready for marketing as a finished product. • The processes include separation and purification, which are collectively referred to as downstream processing. 78
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chapter-12 : BIOTECHNOLOGY AND ITS APPLICATIONS
• Biotechnology is the branch of science dealing with
the technological use of biological process. It employs molecular biology and genetics to create improved agricultural products, food, animal feed, industrial materials and medicines. • Research areas of biotechnology – Following are three research areas of biotechnology. –– Providing the best catalyst in the form of improved organism ; generally a microbe or pure enzyme. –– Creating optimal conditions through engineering for a catalyst to act, and –– Downstream processing technologies to purify the protein/organic compound.
Biotechnological applications in agriculture • There are three options to increase the food production : –– Agrochemical based agriculture; –– Organic agriculture ; and –– Genetically engineered crop - based agriculture. • The Green Revolution succeeded in increasing the food
production but it was not sufficient to feed the growing human population. One solution of this problem is use of genetically modified corps. Genes of plants, bacteria, fungi and animals have been changed by manipulations, therefore, these organisms are called Genetically Modified Organisms (GMO). • GM plants have been useful in many ways. Genetic modification has: –– made crops more tolerant to abiotic stresses (cold, drought, salt, heat). –– reduced reliance on chemical pesticides (pestresistant crops). –– helped to reduce post harvest losses. –– increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil). –– enhanced nutritional value of food, e.g., vitamin ‘A’ enriched rice.
Transgenic plants • Transgenic plants can be obtained by combination of
tissue culture and genetic engineering. Transgenic plants have a natural resistance to herbicides and pests. • The vector used to introduce new genes into plant cells is most often a plasmid from the soil bacterium Agrobacterium tumefaciens. This is the Ti plasmid (tumour inducing
plasmid), so called because in nature, it induces tumours in broad leaf plants. For using Ti plasmid as a vector, researchers have eliminated its tumor causing properties while keeping its ability to transfer DNA into plant cells. Hence, for genetic engineering purposes, Agrobacterium strains are developed in which tumor-forming genes are deleted. These transformed bacteria can still infect plant cells. • The part of Ti plasmid transferred into plant cell DNA, is called the T-DNA. This T-DNA with desired DNA spliced into it, is inserted into the chromosomes of the host plant where it produces copies of itself, by migrating from one chromosomal position to another at random. Such plant cells are then cultured, induced to multiply and differentiate to form plantlets. Transferred into soil, the plantlets grow into mature plants, carrying the foreign gene, expressed throughout the new plant.
Bt Cotton (Insect resistant plant) • Soil bacterium Bacillus thuringiensis produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms some protein crystals. These crystals contain a toxic insecticidal protein. • The Bt toxin protein exists as inactive protoxin but once an insect ingests the inactive toxin it is converted into an active form of toxin due to the alkaline pH of the alimentary canal which solubilise the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of the insect. • Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. • The choice of genes depends upon the crop and targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene named cry. There are numerous genes. Two cry genes cryIAc and cryIIAb have been incorporated in cotton. This genetically modified crop is called Bt cotton as it contains Bt toxin genes against cotton bollworms. Similarly, cryIAb has been introduced in Bt corn to protect the same from corn borer.
Pest resistant plants • A nematode Meloidegyne incognitia infests the roots of
tobacco plants and causes a great reduction in yield. A novel strategy was adopted to prevent this infection that was based on the process of RNA interference (RNAi). RNA interference (RNAi) is the phenomenon of inhibiting activity of a gene through production of sense and antisense RNA. • This method involves a specific mRNA silencing. The
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result was that the parasite could not survive in a transgenic host expressing specific interfering RNA. The transgenic plants thus got itself protected from the parasite. • ‘Flavr savr’ tomato was the first transgenic variety to reach the market. Here inactivation of gene which produces polygalactouronase enzyme has been done. The non-availability of this enzyme prevents overripening because the enzyme is essential for degradation of cell walls. • Golden rice is a transgenic variety of rice (Oryza sativa) which contains good quantities of b-carotene (provitamin A – inactive state of vitamin A). • Production of value added products like nutrition supplements, pharmaceuticals, fuels etc. using transgenic crops (moleular farming).
Biotechnological applications in medicine • The biotechnological processes have made great impact in the area of healthcare by mass production of safe and more effective therapeutic drugs. This is known as medical biotechnology or red biotechnology. • In 1921, Banting and Best along with Macleod succeeded in preparing a pure extract of insulin from the pancreatic islets of a dog. They demonstrated that administration of insulin could cure diabetes in human beings. Later, insulin for curing diabetes used to be extracted from pancreas of slaughtered pigs and cattle. • Insulin is made up of 51 amino acids arranged in two polypeptide chains, A having 21 amino acids and B with 30 amino acids that are linked together by disulphide bridges. In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the prohormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin. The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form.
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1. Induced succession
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2. Diapedesis
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3. Haemozoin
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4. tse tse fly
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5. Dracunculiasis
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• Gene therapy is the technique of genetic engineering
to replace a faulty gene by a normal healthy functional gene. Gene therapy is being tried for sickle cell anaemia and severe combined immuno-deficiency (SCID). The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. • Vaccines represent an invaluable contribution of biotechnology as they provide protection against even such diseases for which effective cures are not yet available. The effectiveness of vaccines may be appreciated from the fact that small pox, once a dreaded disease the world over, has been completely eradicated from the world. • The various vaccines can be grouped under the following types: –– conventional vaccines (live vaccines, inactivated pathogens), –– purified antigen and –– recombinant vaccines (recombinant proteins/ polypeptides, DNA vaccines) • Biotechnology has proved to be a boon in solving crimes, legal disputes, etc. Establishing the identity of victims (e.g., of murder, accidents, etc.), criminals (e.g., in cases of rape, murder, etc.), father (in cases of paternity dispute) etc. is critical to solving the problems of crimes/cases.
Transgenic animals • Many transgenic animals are designed to increase our
understanding of how genes contribute to the development of disease. • Transgenic animals that produce useful biological products can be created by the introduction of the portion of DNA (or genes) which codes for a particular product such as human protein (a-1-antitrypsin) used to treat emphysema. Similar attempts are being made for treatment of phenylketonuria (PKU) and cystic fibrosis. In 1997, the first transgenic cow, Rosie produced human protein-enriched milk (2.4 grams per litre). The milk contained the human alpha-lactalbumin and was
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• •
• •
•
nutritionally a more balanced product for human babies than natural cow milk. Transgenic mice are being developed for use in testing the safety of vaccine before they are used on humans. Transgenic animals are made that carry genes which make them more sensitive to toxic substances than nontransgenic animals. Toxicity testing in such animals will allow us to obtain results in less time. Genetically modified salmon was the first transgenic animal obtained for food production. Transgenic sheep have been produced to achieve better growth and meat production. For example, human genes for blood clotting factor IX and for a1-antitrypsin have been transferred in sheep and expressed in mammary tissue. Dogie is a transgenic dog with excellent smelling power.
Industrial biotechnology • Use of microbes to obtain a product or service of economic
value constitutes industrial biotechnology. It is also known as white or grey biotechnology.
•
•
•
Fuel biotechnology • The use of biological agents to convert relatively diffuse
• • •
•
and inconvenient source of energy (e.g., biomass and sunlight) into more dense and convenient fuels constitutes fuel biotechnology. Biomass is the total cellular dry weight or organic material produced by an organism. It is traditional fuel in the form of coal, gas, oil, wood, Peat and dried animal dung. Biologically produced fuels are usually called biofuels. Often biologically generated hydrogen, methane, diesel are referred to as biohydrogen, biomethane (or biogas) and biodiesel, respectively. Artificial photosynthesis, producing hydrogen gas as a biofuel from water is a longterm process. Biogas is a mixture of methane (50 – 70%) and carbon dioxide (CO2), with traces of nitrogen, hydrogen and other gases. Methanogens (e.g., Methanobacterium) are a group of bacteria or archaebacteria which can produce methane from CO2 and H2. Ethanol (ethyl alcohol) has been produced successfully for use as a fuel in Brazil since 1975.
Ethical issues • Ethics includes rules of conduct by which a community
regulates its behaviour and decides as to which activity is lawful and which is not. Therefore, bioethics includes rules of conduct that may be used to regulate our activities in relation to the biological world. The biosafety guidelines are developed to contribute to ensuring an adequate level of protection in the fields of safe transfer, handling and use of living modified organisms. • It is resulting from modern biotechnology that may
• •
•
have adverse effects on the conservation and sustainable use of biological diversity, and to reduce risks to human health. A patent is the right granted by a government to an inventor to prevent others from commercial use of his invention. When patents are granted for biological entities and for products derived from them, these patents are called biopatents. Patents have been taken out on plants such as black pepper (Piper nigrum), basmati rice (Oryza sativa), Indian mustard (Brassica campestris), pomegranate (Punica granatum), turmeric and neem. Some organisations and multinational companies exploit and/or patent biological resources or bioresources of other nations without proper authorisation from the countries concerned, this is called biopiracy. For example, a patent granted in U.S.A. covers the entire ‘basmati’ rice germplasm indigenous to our country. Bioethics includes rules of conduct that may be used to regulate our activities in relation to the biological world. The main bioethical concerns pertaining to biotechnology are briefly mentioned as follows: –– Introduction of a transgene from one species into another species violates the ‘integrity of species’. –– Biotechnology may pose unforeseen risks to the environment, including risk to biodiversity. –– Transfer of human genes into animals (and vice-versa) dilutes the concept of ‘humanness’. –– When animals are used for production of pharmaceutical proteins, they are virtually reduced to the status of a ‘factory’. –– Use of animals in biotechnology causes great suffering to them. –– It is disrespectful to living beings, and only exploits them for the benefit of human beings. –– Scientists can not rule out the possibility of other biological damage. –– It can accidentally create new infectious agents. All these aspects indicate that biotechnology is focussed on exploiting the biological world. Therefore, we have to decide which activities are ethical and which are not. There has been growing realisation of the injustice, inadequate compensation and benefit sharing between developed and developing countries. Therefore, some nations are developing laws to prevent such unauthorised exploitation of their bio-resources and traditional knowledge. The Indian Parliament has recently cleared the second amendment of the Indian Patents Bill, that takes such issues into consideration, including patent terms emergency provisions and research and development initiative.
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WorldMags.net Practice Questions 1. Identify A, B, C, D in the given diagram of E. Coli cloning vector pBR 322.
(a) (b) (c) (d)
A Hind I Hind I Bam H I Eco RI
B Eco RI Bam H I Pst I Bam H I
C ampR kanR ori ampR
D ori ampR ampR ori.
2. If you want to recover many copies of the target DNA, you will choose a vector (a) which do not have ori gene (b) which have antibiotic resistance gene (c) whose ori supports high copy number (d) which have only one restriction site. 3. Fill up the blanks and select the correct option. (A) Eco RI cuts the DNA between bases _______ only when the sequence _______ is present in the DNA. (B) The growth of bacteriophage in E.coli is restricted through _______ and _______ of its DNA. (C) Disruption of the cell membranes can be acheived by treating the bacterial, plant cells or fungus with enzymes respectively _______, _______ and _______. (D) Since DNA has a _______ charge, it moves towards the _______ of the electrophoretic chamber. (a) (A) - G↓A, GAATTC; (B) methylation, ligation; (C) endonuclease, cellulase, chitinase; (D) negative, anode. (b) (A) - G↓A, GAATTC; (B) methylation, fragmentation; (C) lysozyme, cellulase, chitinase; (D) positive, cathode. (c) (A) - G↓A, GAATTC; (B) - methylation, fragmentation; (C) lysozyme, cellulase, chitinase; (D) negative, anode. (d) (A) - G↓A, GAAATC; (B) - methylation, fragmentation; (C) lysozyme, cellulase, chitinase; (D) positive, cathode. 4. The below flow chart represents the recombinant DNA technology, identify A, B, C and D. 82
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(a) (A)-Restriction endonuclease; (B)-Restriction exonuclease; (C)-DNA ligase; (D)-Transformation (b) (A)-Restriction endonuclease; (B)-Restriction endonuclease, (C)-DNA ligase, (D)-Transformation (c) (A)-Restriction exonuclease, (B)-Restriction endonuclease, (C)-Hydrolase, (D)-Transduction (d) (A)-Restriction endonuclease, (B)-Restriction endonuclease, (C)-Hydrolase, (D)-Transduction. 5. The term “competent” refers to (a) increase the competition between cells (b) making cells impermeable for DNA (c) increase the efficiency with which DNA enters the bacterium through pores in its cell wall (d) making cells permeable for divalent cations. 6. Correct sequence of making a competent cell is (a) treatment with divalent cation → incubation in ice with recombinant DNA → heat shock (42°C) → placing it on ice. (b) heat shock (42°) → incubation in ice with recombinant DNA → treatment with divalent cation → placing it on ice. (c) Treatment with divalent cation → placing it on ice → heat shock (42°C) → incubation in ice with recombinant DNA. (d) incubation in ice with recombinant DNA → heat shock (42°C) → treatment with divalent cation → placing it on ice. 7. How many fragments will generate if you digest a linear DNA molecule with a restriction enzyme having four recognitiion sites on the DNA? (a) 3 (b) 6 (c) 5 (d) 4.
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8. If a person obtains transformants, by inserting a recombinant DNA within the coding sequence of b-galactosidase, he will separate out recombinants from non-recombinants by observing (a) non-recombinant colonies do not produce any colour, whereas recombinants form blue coloured colonies (b) recombinant colonies do not produce any colour, whereas non-recombinants form blue coloured colonies (c) recombinants and non-recombinants both produce blue coloured colonies (d) no colonies are formed due to insertional inactivation 9. Eukaryotic genes do not function properly when cloned into bacterial cell, because (a) of high pH present in bacterial cell (b) of inability to excise introns and destruction by bacterial restriction enzymes (c) of inapropriate insertion of genes (d) both (a) and (b). 10. Which one of the following is not a correct match? (a) Opines – Ti plasmid (b) DNA probing – Searching for desired DNA fragment (c) PCR – DNA staining (d) Agarose – Sea weeds. 11. In recombinant DNA technology insertional inactivation results in (a) inactivation of the host (b) inactivation of the enzyme (c) inactivation of the recombinant DNA (d) inactivation of the host’s snRNA. 12. Which of the following is/are part(s) of biotechnology? A. In vitro ferilization B. Synthesis of a gene C. Correcting a defective gene D. Developing a DNA vaccine. (a) A and B (b) B and C (c) C and D (d) A, B, C and D. 13. Which of the following technique is used to check the progression of a restriction enzyme digestion? (a) Polymerase chain reaction (b) Agarose gel electrophoresis (c) Chromatography (d) None of the above. 14. Select the incorrect match. (a) Golden rice – Vitamine A rich (b) PCR _ Amplification of DNA (c) Cry – Genetically engineered insulin (d) Biotechnology – Genetically modified microbes. 15. Which of the following are the three critical research areas of biotechnology?
(i) Artificial insemination (ii) Providing the best catalyst in the form of improved organism and microbe or pure enzyme. (iii) Inbreeding depression. (iv) Creating optimal conditions through engineering for catalyst to act. (v) Down stream processing. (a) (i), (iii) and (iv) (b) (ii), (iii) and (v) (c) (iv), (v) and (vi) (d) (ii), (iv) and (v). 16. Tailor-made plants generated by genetic modification, (a) are bio-insecticidal plants (b) are heat resistant plant (c) are rich in vitamin A (d) all of these 17. Bt toxin genes have been expressed in plants in order to provide resistance against: (i) Lepidopterans and fungi (ii) Animals and bacteria (iii) Bacteria and fungi (iv) Coleopterans and dipterans (v) Only lepidopterans. (a) (ii) and (iii) (b) (i), (ii) and (iv) (c) (iii) and (v) (d) (iv) and (v). 18. Identify the correct names labelled as W, X, Y and Z in the below diagram of maturation of pro-insulin into insulin.
(a) W - A peptide, X - B-peptide, Y - proinsulin, Z -free C peptide. (b) W - proinsulin, X - A-peptide, Y - B-peptide, Z -free C peptide. (c) W - proinsulin, X - A-peptide, Y - B-peptide, Z-insulin. (d) W - proinsulin, X - free C-peptide, Y - A-peptide, Z - B-peptide. 19. Bt corn is produced to be resistant from corn borer disease by the introduction of gene. (a) cry I Ab (b) cry II Ab (c) ampR (d) cry I Ac. 20. Early detection of a disease is possible by (a) serum and urine analysis (b) gene therapy (c) recombinant DNA technology and ELISA (d) both (a) and (c).
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21. Identify the correct match for the given columns. Column - I Column - II A. Rosie (i) Radio active isotope B. Golden rice (ii) Cry gene C. Bt cotton (iii) Vitamin A D. DNA probe (iv) First transgenic cow. (a) A - (iv), B - (iii), C - (ii), D - (i) (b) A - (i), B - (iii), C - (iv), D - (ii) (c) A - (iv), B - (ii), C - (i), D - (iii) (d) A - (ii), B - (iii), C - (iv), D - (i). 22. Rules of conduct that may be used to regulate our activities in relation to the biological world is called (a) bioethics (b) biowar (c) biopatent (d) biopiracy. 23. Transgenic mice are being used to test the safety of (a) polio vaccine (b) BCG vaccine (c) antitrypsin (d) hepatitis B vaccine. 24. A restriction endonuclease breaks bond between the (a) base pairs of a DNA molecule (b) base pairs of a DNA-RNA hybrid molecule (c) sugar and phosphate components of a nucleic acid molecule. (d) exons and introns of a DNA molecule. 25. Which of the following is/are correct about the process of RNA interference? (i) This is used to prevent the infestation of protozoans. (ii) It takes place in some eukaryotic and all prokaryotic organisms as a method of cellular defense. (iii) The method involves silencing of a specific mRNA due to a complementary dsRNA molecule. (iv) It is novel strategy to produce pest-resistant plants. (a) (iii) & (iv) (b) (ii), (iii) & (iv) (c) (i) & (iii) (d) (iii) only. 26. Identify the correct match for the given apparatus.
Apparatus (a) Gene gun (b) Gene gun (c) Stirred tank bioreactor (d) Stirred tank bioreactor 84
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Function Vectorless direct gene transfer Down processing Culturing method to produce higher yields of proteins Finding out rate of respiration.
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27. Genetic engineering is possible because (a) we can cut DNA at specific sites by endonucleases like type II restriction endonuclease (b) restriction endonucleases purified from virus can be used in bacteria (c) the phenomenon of transduction in bacteria is well understood (d) we can see DNA by electron microscope. 28. Bt toxin gene has been cloned from the bacteria and expressed in plants to provide resistance to insects without the need for insecticides. Select these resistant plants from the given list. (i) Cotton (ii) Corn (iii) Rice (iv) Tomato (v) Potato (vi) Soyabean (a) (i), (ii), (iii) & (iv) (b) (ii), (iii), (iv) & (v) (c) (i), (ii), (v) & (vi) (d) all of these. 29. Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because (a) bacteria are resistant to the toxin (b) toxin exist as toxoid (c) toxin exist as protoxins (d) bacteria encloses toxin in a special sac. 30. What is the permanent cure of adenosine deaminase (ADA) deficiency in children? (a) Bone marrow transplantation. (b) Enzyme replacement therapy in which functional ADA is given to patient by injection. (c) Infusion of genetically engineered lymphocytes (in which functional ADA - cDNA is introduced) into the patient’s blood. (d) Introduction of gene isolated from bone marrow cells producing ADA, into cells at early embryonic stages. 31. The transfer of genetic material from one bacterium to another by virus is called (a) translation (b) conjugation (c) transduction (d) transformation. 32. Streptomycin is obtained from (a) Streptomyces griseus (b) S. aureofaciens (c) S. venezuelae (d) S. ramosus. 33. Bt cotton is resistant to (a) insects (b) herbicides (c) salt resistant (d) drought resistant. 34. The transgenic animals are those which have (a) foreign RNA in all its cells (b) foreign DNA in some of its cells (c) foreign DNA in all its cells (d) both (a) and (b). 35. Polymerase chain reaction makes use of a DNA polymerase enzyme which is (a) a terminal transferase (b) thermolabile (c) thermostable (d) modular enzyme.
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WorldMags.net It is a matter of great satisfaction and encouragement to realise that our efforts in “Excel in Physics, Excel in Chemistry and Excel in Biology” have received overwhelming response. Nearly all the questions asked in the CBSE Board Examination 2012 were available in the books; fully solved. We feel pleased to present the revised edition of the books. The books give comprehensive account of the subject according to the current syllabus and pattern of the CBSE Board Examination. This will impart the students a clear and vivid understanding of the subject matter.
Available at leading bookshops throughout India.
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36. The enzyme used in polymerase chain reaction (PCR) is (a) Taq polymerase (b) RNA polymerase (c) ribonuclease (d) endonuclease. 37. The genetically-modified (GM) brinjal in India has been developed for (a) insect-resistance (b) enhancing shelf life (c) enhancing mineral content (d) drought-resistance. 38. Satellite DNA is useful tool in (a) organ transplantation (b) sex determination (c) forensic science (d) genetic engineering. 39. Which of the following is not used as bioweapon? (a) Bacillus anthracis (b) Botulinum toxin (c) Bacillus thuringiensis toxin (d) Smallpox. 40. Bacillus thuringiensis forms protein crystals which contain insectidical protein. This protein (a) binds with epithelial cells of midgut of the insect pest ultimately killing it (b) is coded by several genes including the gene cry (c) is activated by acid pH of the foregut of the insect pest (d) does not kill the carrier bacterium which is itself resistant to this toxin. 41. The term “molecular scissors” generally refers to (a) DNA polymerases (b) RNA polymerases (c) restriction endonucleases (d) DNA ligases. 42. The purpose of polymerase chain reaction is (a) DNA modification (b) DNA amplification (c) DNA replication (d) DNA visualization. 43. Plasmids are (a) extra chromosomal DNA which can self replicate (b) DNA carrying genetic sequence, without expressing it (c) integrated within host DNA without replication ability (d) none of these. 44. Consumption of which one of the following foods can prevent the kind of blindness associated with vitamin ‘A’ deficiency? (a) ‘Flavr Savr’ tomato (b) Canolla (c) Golden rice (d) Bt-Brinjal. 45. For transformation, micro-particles coated with DNA to be bombarded with gene gun are made up of (a) silver or platinum (b) platinum or zinc (c) silicon or platinum (d) gold or tungsten. 46. Tobacco plants resistant to a nematode have been 86
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developed by the introduction of DNA that produces (in the host cells) (a) both sense and anti-sense RNA (b) a particular hormone (c) an antifeedant (d) a toxic protein. 47. Which one of the following represents a palindromic sequence in DNA? (a) 5′ - GAATTC - 3′ (b) 5′ - CCAATG - 3′ 3′ - CTTAAG - 5′ 3′ - GAATCC - 5′ (c) 5′ - CATTAG - 3′ (d) 5′ - GATACC - 3′ 3′ - GATAAC - 5′ 3′ - CCTAAG - 5′ 48. Read the two statements A and B and identify the correct circle from those given below. Statement A : Agrobacterium tumefaciens is the causative agent of crown gall disease of dicots. Statement B : Agrobacterium tumefaciens causes infection by entering the plant through wounds and injuries. (a) Statement A is correct and B is wrong. (b) Statement B is correct and A is wrong. (c) Both statements A and B are correct. (d) Both statements A and B are wrong. 49. The usual source of restriction endonucleases used in gene cloning is (a) fungi (b) bacteria (c) plants (d) viruses. 50. Gel electrophoresis is used for the (a) separation and isolation of DNA fragments (b) construction of recombinant DNA by joining with cloning vectors (c) culturing the host cells in a medium at a large scale (d) replication of DNA for many times 51. RNA interference is essential for the (a) cell proliferation (b) cell defence (c) cell differentiation (d) micropropagation. 52. The figure below shows three steps (A, B, C) of Polymerase Chain Reaction (PCR). Select the option giving correct identification together with what it represents?
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B O O K S
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(a) B - denaturation at a temperature of about 98°C separating the two DNA strands. (b) A - denaturation at a temperature of about 50°C. (c) C - extension in the presence of DNA polymerase. (d) A - annealing with two sets of primers. 53. The Bt toxin is not toxic to human beings because (a) the pro Bt toxin activation requires temperature above human body temperature. (b) the Bt toxin recognizes only insect-specific targets. (c) the Bt toxin formation from pre Bt toxin requires pH lower than that present in human stomach. (d) conversion of pro Bt toxin to Bt toxin takes place only in highly alkaline conditions. 54. The thermostable enzymes, ‘Taq’ and ‘Pfu’, isolated from thermophilic bacteria are (a) RNA polymerases (b) DNA polymerases (c) restriction endonucleases (d) DNA ligases. 55. Bt brinjal is an example of transgenic crops. In this, Bt refers to (a) Bacillus tuberculosis (b) biotechnology (c) b carotene (d) Bacillus thuringiensis. 56. Which of the following is not correct statement about the plasmids ? (a) It is the extra chromosomal DNA in bacteria. (b) It is not an integral part but inert genetic material. (c) Host chromosome can be integrated with the plasmid. (d) Transfer of plasmid can be done from cell to cell without killing the host. 57. Stirred-tank bioreactors have been designed for (a) addition of preservatives to the product (b) purification of the product (c) ensuring anaerobic conditions in the culture vessel (d) availability of oxygen throughout the process. 58. Plants in comparison to animals are more rapidly manipulated by genetic engineering. Select out the most probable reason for this (a) totipotency shown by plant cells (b) single somatic cell can regenerate a whole plant body (c) genetic engineering is supplemented with plant tissue culture techniques (d) all of the above. 59. The technique in which foreign DNA is precipitated over surface of metal particles for passing into target cells is (a) microinjection (b) electroporation (c) particle gun (d) chemical mediated gene transfer. 88
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60. Insulin has 51 amino acids arranged in (a) single polypeptide (b) two polypeptides of 21 and 30 amino acids (c) two polypeptides of 25 and 26 amino acids (d) three polypeptides having 15, 16 and 20 amino acids. 61. Crown gall disease in plants is caused by (a) Ti plasmid (b) Pi plasmid (c) bacteria (d) virus. 62. Two microbes found to be very useful in genetic engineering are (a) crown gall bacterium and Caenorhabditis elegans (b) Escherichia coli and Agrobacterium tumefaciens (c) Vibrio cholerae and a tailed bacteriophage (d) Diplococcus sp. and Pseudomonas sp. 63. Human insulin is being commercially produced from a transgenic species of (a) Rhizobium (b) Saccharomyces (c) Escherichia (d) Mycobacterium. 64. In transgenics, expression of transgene in target tissue is determined by (a) enhancer (b) transgene (c) promotor (d) reporter. 65. Recombinant DNA technology is related with (a) C. Darwin (b) Stanley Cohen (c) Herbert Boyer (d) Both (b) and (c). 66. Transgenic crop contains (a) gene for resistance to antibiotics (b) protein produced by the gene (c) enzymes produced by the gene for antibiotics (d) all of the above. 67. cDNA is (a) formed by reverse transcriptase (b) cloned DNA (c) circular DNA (d) recombinant DNA. 68. Electroporation involves (a) promotion of seed germination by induced imbibition of water with electric current (b) making transient pores in cell membrane to facilitate entry of gene constructs (c) purification of saline water with the help of an artificial membrane (d) passage of sucrose through sieve pores by electroosmosis. 69. Restriction endonuclease enzyme cuts (a) any fragment of DNA (b) (+) fragment of DNA (c) (–) fragment of DNA (d) double helical DNA.
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70. The two main vectors used in genetic engineering to carry genes into bacteria are (a) plasmids and bacteriophages (b) plastids and plasmids (c) plastids and bacteriophages (d) plasmids and phasmids. 71. Plant cells can be converted to protoplasts by treating them with (a) cellulase (b) cellulase + pectinase (c) cellulase + pectinase + lipase (d) cellulase + pectinase + lipase + protease. 72. Gene therapy involve (a) introduction of a normal genes in cell (b) treating of defective genes with radiation (c) eliminating defective and useless genes (d) replacement of defective genes by normal one.
73. The separated DNA fragments can be visualized with a compound known as (a) lysozyme (b) agarose gel (c) ethidium bromide (d) Ti plasmid 74. Which of the following is a palindromic sequence? (i) HANNAH (ii) TESTREST (iii) SEXES (iv) MUNMUN (a) (i) and (iii) (b) (ii) and (iv) (c) (i), (iii) and (iv) (d) all of these 75. Transformation procedure can be identified with the help of selectable markers which are (a) origin of replication genes (b) recognition sites (c) cloning sites (d) antibiotic resistance genes 76. DNA ligase form ‘X’ between adjacent nucleosides and covalently link two individual fragments of double – stranded DNAs. What is ‘X’? (a) Phophodiester bonds (b) Hydrogen bonds (c) Disulphide bonds (d) Glycosidic bonds 77. Attempts are being made to produce useful biological products for the treatment of which of these diseases? (a) Phenylketonuria (b) Cystic fibrosis (c) Emphysema (d) All of these. 78. Read the steps involved in the technique of ELISA and arrange these steps in correct sequence. (i) Unreacted anti-Ig is washed away. (ii) Antigen of interest immobilized on the surface Petriplate. (iii) Anti-Ig binds to Ag-Ab complex.
(iv) Unreacted molecules of Ag-Ab complex are washed away. (v) Antibody specific to the Ag reacts with it. (vi) substrate is added to react with enzyme conjugated with anti-Ig. (a) (ii), (v), (iv), (iii), (i), (vi) (b) (ii), (iv), (v), (iii), (i), (vi) (c) (iv), (v), (ii), (vi), (iii), (i) (d) (ii), (v), (iv), (i), (iii), (vi)
79. Which of the following is not the application of transgenic animals? (a) Developing animals specially created for use in xenografting. (b) Molecular diagnosis of pathogens such as detecting presence of antigens, their proteins or glycoproteins, etc. (c) To test genetically engineered hormones to increase milk yield, meat production, etc. (d) To test pharmaceutical proteins,, drugs production etc. 80. The Ti plasmid of Agrobacterium tumifaciens has now been modified into a cloning vector after ‘disarming’ it. Which property of it is useful as a cloning vector? (a) It delivers genes of interest into a variety of plants. (b) It possesses sites for insertion of foreign gene which is to be introduced. (c) It possesses selectable markers. (d) All of these.
Answer key 1. (d) 6. (a) 11. (b) 16. (d) 21. (a) 26. (c) 31. (c) 36. (a) 41. (c) 46. (a) 51. (b) 56. (b) 61. (a) 66. (d) 71. (b) 76. (a)
2. (c) 7. (c) 12. (d) 17. (d) 22. (a) 27. (a) 32. (a) 37. (a) 42. (b) 47. (a) 52. (a) 57. (d) 62. (c) 67. (a) 72. (d) 77. (d)
3. (c) 8. (b) 13. (b) 18. (b) 23. (a) 28. (d) 33. (a) 38. (c) 43. (a) 48. (c) 53. (d) 58. (d) 63. (c) 68. (b) 73. (c) 78. (a)
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4. 9. 14. 19. 24. 29. 34. 39. 44. 49. 54. 59. 64. 69. 74. 79.
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(b) (b) (c) (a) (c) (c) (c) (c) (c) (b) (b) (c) (d) (d) (a) (b)
5. 10. 15. 20. 25. 30. 35. 40. 45. 50. 55. 60. 65. 70. 75. 80.
(c) (c) (d) (c) (a) (d) (c) (a) (d) (a) (d) (b) (d) (a) (d) (d)
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