Genetics - Bio 12 UP Diliman Reviewer

Friday: Genetics Lec exercises I. Problem Solving 1. Imagine you are a genetic counselor, and a couple planning to start a family came to you for information. Charles was married once before, and he and his first wife had a child who has cystic fibrosis. The brother of his current wife Elaine died of cystic fibrosis. What is the probability that Charles and Elaine will have a baby with cystic fibrosis? (Neither Charles nor Elaine has the disease) 2. In mice, black color (B ) is dominant to white (b ). At a different locus, a dominant allele (A ) produces a band of yellow just below the tip of each hair in mice with black fur. This gives a frosted appearance known as agouti. Expression of the recessive allele (a ) results in a solid coat color. If mice that are heterozygous at both loci are crossed, what will be the expected phenotypic ratio of their offspring? 3. The pedigree below traces the inheritance of a very rare biochemical disorder in humans. Affected individuals are indicated by filled-in circles and squares. Is the allele for this disorder dominant or recessive? What genotypes are possible for the individuals marked 1, 2, and 3.

4. In 1981, a stray black cat with unusual rounded curled-back ears was adopted by a family in California. Hundreds of descendants of the cat have since been born, and cat fanciers hope to develop the "curl" cat into a show breed. Suppose you owned the first curl cat and wanted to develop a true breeding variety. a. How would you determine whether the curl allele is dominant or recessive? b. How would you select for true-breeding cats? c. How would you know they are true-breeding? 5. Given the ff:

a. What proportion of the progeny will be AAbbCcDDeeFf? b. What is the probability of having at least one dominant trait? 6. In the F2 progeny from a monohybrid cross, what is the proportion of heterozygotes among the dominant progeny? 7. A phenotypically normal man, who has a hemophiliac brother, marries a normal woman, who is not a carrier. What is the probability that any of their children will be hemophiliac?

8. In man, optic atrophy (a type of blindness due to a defective optic nerve) is controlled by a sexlinked, recessive gene. Aniridia (a type of blindness due to the absence of the iris) is controlled by a dominant autosomal (not sex-linked) gene. A woman who is blind from optic atrophy marries a man who is blind from aniridia, whose father was not blind. What types of children can they have? (use the letter “b” for optic atrophy and the letter “A” for aniridia) 9. A man files his wife for divorce on the grounds of infidelity. Both man and wife have normal eyes, but there is a baby daughter who has coloboma iridis (a fissure in the iris of the eye). This characteristic is known to be inherited as a sex-linked, recessive trait. If you were the man’s lawyer, could you use this fact as evidence? If so, how would you explain the case to the jury? 10. Coat color in cats is a co-dominant trait and is also located on the X chromosome. Cats can be black, yellow or calico. A calico cat has black and yellow splotches. In order to be calico, the cat must have an allele for the black color and an allele for the yellow color. Use a punnet square to show why there are no male calico cats. (use the letter “Y” for yellow and “B” for black) 11. A female calico cat is crossed with a male black cat. What are the phenotypes of the offspring? 12. In the 1950’s, a young woman sued film star/director Charlie Chaplin for parental support of her illegitimate child. Charlie Chaplin’s blood type was already on record as type AB. The mother of the child had type A and her son had type O blood a. Complete a Punnett square for the possible cross of Charlie and the mother. b. The judge ruled in favor of the mother and ordered Charlie Chaplin to pay child support costs of the child. Was the judge correct in his decision based on blood typing evidence? Explain why or why not. *refer to any Punnett squares to support your answer. 13. Baldness is a sex-linked trait. a. What parental genotypes could produce a bald woman? b. What parental genotypes could produce a bald man? 14. A blue-eyed man (1) whose parents were brown eyed (2 & 3), marries a brown eyed woman (4), whose father was brown eyed (5) and whose mother (6) was blue eyed. They have one female child who is blue eyed (7). Blue eyes are recessive. a. Make a pedigree chart based on the above information. b. Label the genotypes of the individuals in the chart. 15. Scale coloration of lizards has a complete dominance relationship where green scales are dominant over blue scales. There are 1,024 individuals with the genotype GG, 512 individuals with the genotype Gg, and 64 individuals with the genotype gg. Find: the frequency of the dominant and recessive alleles and the frequency of individuals with dominant, heterozygous, and recessive genotype.

II. Multiple Choice 1. A dwarf plant can be induced to reach normal height by the application of: A. Auxins B. Cytokinins C. Gibberellins D. Ethylene 2. A ripe Avocado will cause other avocados to ripen through the release of: A. Auxin B. Ethylene C. Abscissic Acid D. Gibberellin 3. Seedless fruits can be produced by the application of auxin or: A. Cytokinin B. Gibberellin C. Ethylene D. Oligosaccharin 4. Substances that stimulate cell division and cause dormant seeds to sprout are: A. Gibberellins B. Cytokinins C. Abscissic Acid D. IAA 5. Unlike tropisms, nastic movements are in response to A) darkness B) wind C) non-directional stimuli D) directional stimuli 6. The pathway leading to flowering for plants that requires vernalization is the A) seasonal pathway B) light-dependent pathway C) temperature-dependent pathway D) autonomous pathway 7. Roots grow downward as a weak _______________ response. A) negative phototropic B) positive phototropic C) negative gravitropic D) negative thigmotropic E) positive thigmotropic 8. Environmental signals influence the distribution of an auxin in a plant by A) decreasing the cell's sensitivity to the auxin B) causing auxin to migrate to the lighted portion C) destroying the auxin D) causing auxin to migrate into the shaded portion E) causing the plant to produce more auxin 9. Which of the following plant hormones in incorrectly paired with its function? A) auxins -- responsible for apical dominance B) abscissic acid -- regulates the rate of transpiration

C) D) E)

cytokinins -- delays senescence (aging and decay) ethylene -- promotes ripening gibberellins -- promotes bud and seed dormancy

10. Although abscisic acid in not involved in the formation of the abscission layer, it does have many roles in the life of plants. Which of the following is not a function of abscisic acid? A) B) C) D) E)

In times of water stress, it causes the stomata to close. It promotes tolerance to stress. It induces dormancy of buds. It induces leaf and flower senescence. It induces and maintains the dormancy of seeds.

11-12. For the ff. pair of items, choose an option that best describe the relationship. A) Item (A) is greater than item (B). B) Item (A) is less than item (B). C) Item (A) is exactly or very approximately equal to item (B). D) Item (A) may stand in more than one of the above relations to item (B). 11. (A) The number of cells within the embryo sac (B) The number of nuclei within the embryo sac 12. (A) The ploidy of the angiosperm seed endosperm (B) The ploidy of the angiosperm seed embryo 13. Plants growing in a partially dark environment will grow toward light in a response called phototropism. Choose the incorrect statement regarding phototropism. A) It is caused by a chemical signal. B) One chemical involved is auxin. C) Auxin causes a growth increase on one side of the stem. D) Auxin causes a decrease in growth on the side of the stem exposed to light. E) Removing the apical meristem prevents phototropism. 14. Which of the following is not presently considered a major mechanism whereby hormones control plant development? A) affecting cell respiration via regulation of the citric acid cycle B) affecting cell division via the cell cycle C) affecting cell elongation through acid growth D) affecting cell differentiation through altered gene activity E) mediating short-term physiological responses to environmental stimuli 15. According to modern ideas about phototropism in plants, A) light causes auxin to accumulate on the shaded side of a plant stem. B) auxin stimulates elongation of plant stem cells. C) auxin is produced by the tip of the coleoptile and moves downward.

D) A and B only E) A, B and C 16. After some time, the tip of a plant that has been forced into a horizontal position grows upward. This phenomenon is related to A) light. B) whether the plant is in the northern or southern hemisphere. C) gibberellin production by stems. D) auxin production in roots. E) auxin movement toward the lower side of the stem. 17. The ripening of fruit and the dropping of leaves and fruit are principally controlled by A) auxins B) cytokinins C) indole acetic acid D) ethylene E) carbon dioxide concentration (in air) 18. Which one of the following is not a direct function of either auxin or gibberellin? A) inducing semescence and ripening B) producing apical dominance C) producing positive geotropism of shoots D) stimulating cell elongation E) breaking dormancy in seeds 19. Which of the following statements about plant hormones is false? A) The growth of plants in nature is probably regulated by a combination of growth-stimulating and growth-inhibiting hormones. B) Abscisic acid generally promotes growth. C) Gibberellins stimulate cell enlargement. D) Cytokinins promote cell division. E) Ethylene contributes to the aging of plants 20. When growing plants in culture, IAA is used to stimulate cell enlargement. Which plant growth regulator has to now be added to stimulate cell division? A) ethylene B) indoleacetic acid C) gibberellin D) cytokinin E) abscisic acid 21. Plant growth regulators can be characterized by all of the following except that they A) may act by altering gene expression. B) have a multiplicity of effects. C) function independently of other hormones. D) control plant growth and development.

E) affect division, elongation, and differentiation of cells. 22. Why might animal hormones function differently from plant hormones? A) Animals move rapidly away from negative stimuli, and most plants donʹt. B) Plant cells have a cell wall that blocks passage of many hormones. C) Plants must have more precise timing of their reproductive activities. D) Plants are much more variable in their morphology and development than animals. E) Both A and D are correct. 23. Buds and sprouts often form on tree stumps. Which of the following hormones would you expect to stimulate their formation? A) auxin B) cytokinins C) abscisic acid D) ethylene E) gibberellins 24. How does indoleacetic acid affect fruit development? A) preventing pollination B) inhibiting formation of the ovule C) promoting gene expression in cambial tissue D) promoting rapid growth of the ovary E) inducing the formation of brassinosteroids 25. The heavy line in Figure 39.1 illustrates the relationship between auxin concentration and cell growth in stem tissues. If the same range of concentrations were applied to lateral buds, what curve would probably be produced? A) I B) II C) III D) II and III E) either I or III 26. The results of this experiment, shown on the left of the graph (area A), may be used to A) show that these plants can live without gibberellin. B) show that gibberellin is necessary in positive gravitropism. C) show that taller plants with more gibberellin produce fruit (pods). D) show a correlation between plant height and gibberellin concentration. E) study phytoalexins in plants. 27. Based on no. 26, this experiment suggests that the unknown amount of gibberellin in the experimental plant (B) is approximately

A) zero. B) 0.01 μg/mL. C) 0.1 μg/mL. D) 1.0 μg/mL. E) equal to the amount of gibberellin in the shortest plant. 28. In attempting to make a seed break dormancy, one logically could treat it with A) IAA. B) 2, 4-D. C) CO2. D) gibberellins. E) abscisic acid. 29. Ethylene, as an example of a plant hormone, may have multiple effects on a plant, depending on all of the following except the A) site of action within the plant. B) developmental stage of the plant. C) concentration of ethylene. D) altered chemical structure of ethylene from a gas to a liquid. E) readiness of cell membrane receptors for the ethylene. 30. We tend to think of plants as immobile when, in fact, they can move in many ways. All of the following are movements plants can accomplish except A) growth movements up or down in response to gravity. B) folding and unfolding of leaves using muscle-like tissues. C) growth movements toward or away from light. D) changes in plant growth form in response to wind or touch. E) rapid responses using action potentials similar to those found in the nervous tissue of animals.