NMAT Review Biochem, Genetics and Central Dogma

10/17/15  

Biochemistry

National Medical Admission Test (NMAT) review:

Biology Prepared by Joshua Evans M. Bajao

Macromolecules Ø 

Simply put, a very large molecule that is necessary for life.

Ø 

Created by the polymerization of smaller subunits called monomers.

Ø 

4 Types of the most important Macromolecules Lipids Carbohydrates

Macromolecules: Lipids A group of naturally occurring non-polar molecules that contain hydrocarbons. ž  Glycerol and fatty acids are the monomers of lipids. ž 

fatty acid

Nucleic Acids Proteins glycerol

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Macromolecules: Lipids ž 

Main function of lipids include energy storage, signaling, and structural components of the cell memrabe (Phospholipids).

Macromolecules: Carbohydrates ž  One

of the main types of nutrients. is the monomer of carbohydrates. ž  Polysaccharides may serve as a storage for energy and or structural components. ž  Includes sugars, starch, cellulose, etc. ž  Monosaccharides

Macromolecules: Carbohydrates

Macromolecules: Proteins

ž  Three

ž 

of the most common disaccharides

ž  ž 

Are large biomolecules that perform a vast array of functions within the organism. Composed of one or more chains of amino acid residues, the monomer for proteins. The structure of an amino acid consist of one carbon with a carboxylic acid and an amine group

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Macromolecules: Proteins

Macromolecules: Nucleic acids Are Macromolecules composed by nucleotides. ž  Nucleotides consist of a nitrogenous bases (Adenine, Thymine, Guanine, Cytosine), a fivecarbon sugar backbone (deoxyribose for DNA, ribose for RNA), and a phosphate group. ž 

CELLS

Cell ž  Cell

is the smallest, most basic structural, functional, and biological unit of life. ž  Every organism is compose of one (unicellular organims) or more (multicellular organism) cell. ž  It is the smallest unit of life capable of replicating/reproducing itself independently.

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Cell Theory ž  The

cell is the most basic unit of life.

Two types of Cells Prokaryote

Eukaryote

ž  All

living organisms are composed of one or more cells.

ž  All

cells arise from pre-existing, living cells,

Matthias Schleiden and Theodore Schwann

Prokaryote Anatomy

The main difference is that eukaryotic cell have membrane bound organelles.

Eukaryote Anatomy

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Summary:

Summary:

Difference between Eukaryote and Prokaryote

Difference between Eukaryote and Prokaryote

Prokaryote

Eukaryote

Size

~0 .2-2µm

~ 10-100µm

Location of genomic material (DNA)

Nucleoid region

Membrane bound nucleus

DNA

Single, Circular, lack histones

More than one, linear, with histones (protein)

Prokaryote Motility

Flagella

Rotating Flagella (some)

Eukaryote Undulating Flagella, Cilia (microtubule arranged in a 9+2 manner), and or Pseudopodia

Some (made of flagellin)

some (made of microtubule)

Membrane bound organelles

Absent

Present

Cilia

Absent

Some (made of microtubule)

RNA/protein synthesis

RNA and proteins: Cytoplasm

RNA: Nucleus (nucleolus) Protein: Cytoplasm (free ribosome/RER)

Fimbrae and Pili

Some

Absent

Cell Wall

Most, made of peptidoglycan

Most, cellulose for plants, chitin for fungi

80S Small subunit: 60S Large subunit: 40S

ATP production (etransport chain)

Cell membrane

Mitochondria

Mode of reproduction

Binary Fission (asexual) Conjugation (sexual)

Mitosis (asexual) Meiosis (gamete production)

Robosome subunit

70S Small subunit: 50S Large subunit: 30S

Cell Cycle

Mitosis

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Mitosis

Meiosis I

Meiosis II

Meiosis II: detailed

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Meiosis II: detailed

Genetics

Genetics

Genetic terms

ž  Is

Gene – a stretch of DNA that determines a certain trait. ex: Eye Color, Skin color Allele – a specific variation of a gene. ex: Blue eyes, green eyes, black skin, white skin

the study of genes, heredity and genetic variations among species. ž  Gregor Johann Mendel, a scientist and an Augustinian friar, is said to be the father of modern genetics due to his studies regarding the pea plants.

Dominant alleles – are alleles that show their effect even if the individual has only one copy of the said allele. Recessive alleles – are alleles that show their effect only if the individual has two copies of the said allele.

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Genetic terms Homozygous – a genetic condition where an individual inherits the same alleles for a particular gene from both parents. ex: AA, TT, yy, gg Heterozygous – a genetic condition where an individual inherits two different alleles of a particular gene from both parents. ex: Aa, Tt, Yy, Gg Genotype – the organism’s genetic makeup Phenotype – the organism’s observable characteristic or trait

Mendelian Inheritance

Mendelian Inheritance (Laws) Law

Definition

Law of Segregation

During gamete formation, the allele of each gene segregate from each other so that each gametes carries only one copy of the said gene

Law of Independent Assortment

Genes for different trait segregate independently from each other during gamete formation

Law of Dominance

Some alleles are dominant while other are recessive. An organism with atleast one dominant allele will display the phenotype of the said allele

Mendelian Inheritance If a pure bred yellow seeded pea plant was crossed with another pea plant with a green seeds: a)  What is the genotypic ratio of the F2 generation? b)  What is the phenotypic ration of the F2 generation

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Mendelian Inheritance YY Gametes produced:

X

Y

Y

Yy

Yy

X

Mendelian Inheritance Yy

yy y

y

Yy

Yy

Gametes produced:

X

Y

y

YY

Yy

Punnett square Punnett square

Yy

X

Y

y

Yy

yy

Y

y

Y

Y

Y

YY

Yy

y

Yy

Yy

y

Yy

yy

y

Yy

Yy

Mendelian Inheritance If a round yellow seeded pea plan that is heterozygous on both traits were crossed to a pea plant with the same genotype: a)  What is the chance that the offspring will have a green seed that is wrinkled? b)  What is the chance that the offspring will have a yellow seed that is wrinkled? Yellow (Y) is dominant over green and round (R) is dominant over wrinkled.

a) Genotypic ratio is 1YY:2Yy:1yy b) Phenotypic ration: 3 Yellow: 1 Green

Mendelian Inheritance YyRr x YyRr YR Yr yR yr x YR Yr yR yr YR

Yr

yR

yr

YR

YYRR

YYRr

YyRR

YyRr

Yr

YYRr

YYrr

YyRr

Yyrr

yR

YyRR

YyRr

yyRR

yyRr

yr

YyRr

Yyrr

yyRr

yyrr

*Bold letter signifies the round phenotype

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Mendelian Inheritance YyRr x YyRr YY Yy Yy yy : RR Rr Rr rr YY = ¼; Yy = 2/4; yy = ¼: RR = ¼; Rr = 2/4; rr = ¼ a) Green seed that is wrinkled = yyrr yyrr = ¼(yy) x ¼(rr) = 1/16 b) Yellow seed that is wrinkled = Y_rr Y_ = YY + Yy = ¼ + 2/4 = ¾ Y_rr = ¾(Y_) x ¼ (rr) = 3/16

Mendelian Inheritance Two pea plants were crossed, there genotypes are as follows: TtRRYy and ttRrYy (T= tall is dominant to short; R= rounded seed is dominant to wrinkled; Y= yellow seed is dominant to green). a) What fraction of the progeny will be tall, and has a yellow wrinkled seed? b) What about short with green round seed?

Non-Mendelian Inheritance

Incomplete dominance

Sometimes called as Neo-mendelian, is any pattern of inheritance that doesn’t confirm to Mendel’s law of inheritance.

A type of dominance that occur when the phenotype of the heterozygous is distinct, or often an intermediate, to phenotype of both homozygous alleles.

Examples of Non-Mendelian Inheritance Incomplete dominance Codominance Multiple allele Sex-linked

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Codominance

Multiple allele

A type of dominance that occur when both alleles are expressed equally and is visible as a phenotype.

A type of non-Mendelian inheritance pattern that involves more than just the typical two alleles that usually code for a certain phenotype in a species.

Multiple allele

Sex-linked gene

ž  Cross

ž 

between AaBbCc x aaBbCC. What is the chance that the offspring are light colored? —  Aa aa; BB Bb Bb bb; CC Cc —  Aa –

½(Aa) x ¼(bb) x ½(Cc) = 1/16

—  aa – CC – ½(aa) x ¼(bb) x ½(CC) = 1/16

Cc – ½(aa) x 2/4(Bb) x ½(Cc) = 2/16 Light colored = 1/16 + 1/16 + 2/16 = 4/16 = ¼

These are genes, thus, also the allele, that are found in the X chromosomes alone. ž  The result is that the females will have two copies of the sex-linked gene while males will only have one copy of the gene. ž  Females that have a heterozygous allele of a recessive trait in their genotype are called Carriers.

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Sex-linked gene (example) Red-green color blindness is a recessive X-linked gene abnormality. Suppose a normal female carrier (XCXc) has married a normal male (XCY). a)  What is the Genotypic ratio of their offspring. b)  What is the Phenotypic ratio of their offspring.

Sex-linked gene (example) XCXc x XCY XCXC XCY XcXC XcY a)  b) 

1 normal female: 1carrier female: 1 normal male: 1 color blind male 2 normal female: 1 normal male: 1 color blind male

Central Dogma of Molecular Biology

Central Dogma of Molecular Biology

Replication DNA

process of producing two identical DNA from one original DNA template

Transcription RNA

Process of copying the DNA template into an RNA

Translation Protein

Translating the RNA code into a protein sequence

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Replication

Replication

Replication Enzymes

Function

TopoIsomerase

Relaxes the DNA from its super-coiled nature

Helicase

Unwinds the DNA helix at the replication fork

Single Strand Binding (SSB) protein

Bind to ssDNA (single stranded DNA) to prevent it from re-annealing (binding) after DNA helicase unwinds it

DNA primase

Provides a starting point of RNA (or DNA) for DNA polymerase to begin synthesis of the new DNA strand

DNA polymerase

Builds a new DNA strand by adding nucleotides in a 5’ to 3’ direction. Also performs proof reading and error correction.

DNA ligase

Re-anneals the semi-conservative strands and joins the Okazaki Fragments of the lagging strand.

Transcription

Always remember, both strand of DNA double helix complements each other Purines A = T Pyrimidines G = C 5’ ATG GAG CCA GCA TCG GAT TAA 3’! 3’ TAC CTC GGT CGT AGC CTA ATT 5’! Thus, A + G = T + C Note: RNA polymerase doesn’t need a primer to propagate Only one strand is transcribed (template strand) Need a promoter region

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Transcription

Transcription Always remember, like DNA, RNA complements the template DNA, with one exemption: Thymine is absent in RNA. Instead, Uracil (U) complements Adenosine (A).

DNA template 5’ ATG GAG CCA GCA TCG GAT TAA 3’! 3’ UAC CUC GGU CGU AGC CUA AUU 5’ ! ! ! RNA

Translation

Translation – coding

ž  Translation

occur in the ribosomes ž  There are three kinds of RNA responsible for translation —  mRNA – (messenger RNA) RNA that is

transcribed

—  tRNA – (transfer RNA)RNA that holds the

amino acid

—  rRNA – (ribosomal RNA) One of the

constituents of ribosomes, together with various proteins.

5’ AUG GAG CCA GCA UCG GAU UAA 3’! Met Glu Pro Ala Ser Asp stop!

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Translation

Translation

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