Population Genetics PDF

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Supplemental questions for chapter 18: population genetics....

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SUPPLEMENTAL QUESTIONS – CHAPTER 18 1. Consanguineous marriages often lead to A. B. C. D. E.

inbreeding. gene pools. sibling species. an increase in heterozygosity as a rule. hybrid vigor.

Answer: A

2. What term is given to the total genetic information carried by all members of a population? A. B. C. D. E.

gene pool genome chromosome complement breeding unit race

Answer: A 3. In a population of 100 individuals, 49% are of the NN blood type. What percentage is expected to be MN assuming Hardy-Weinberg equilibrium conditions? A. B. C. D. E.

9% 21% 42% 51% insufficient information to answer this question

Answer: C 4. Albinism is an autosomal recessive trait in humans. Assume that there are 100 albinos (aa) in a population of 1 million. How many individuals would be expected to be homozygous normal (AA) under equilibrium conditions? A. B. C. D. E.

19,800 100 980,100 999,900 10,000

Answer: C

5. In small isolated populations, gene frequencies can fluctuate considerably. The term that applies to this circumstance is A. B. C. D. E.

genetic isolation. allelic separation. natural selection. stabilizing selection. genetic drift.

Answer: E 6. The discipline within evolutionary biology that studies changes in allele frequencies is known as A. population genetics. B. consanguineous. C. hybrid vigor. D. genetics. E. cytogenetics. Answer: A 7. Assume that a trait is caused by the homozygous (or hemizygous) state of a gene that is recessive and X-linked. Nine percent of the females in a given population express the phenotype caused by this gene. What percentage of males would be expected to express this trait? Answer: 30% 8. In a population that meets the Hardy-Weinberg equilibrium assumptions, 81 percent of the individuals are homozygous for a recessive gene. What percentage of the individuals would be expected to be heterozygous for this gene in the next generation? Answer: 18%

9. In a population of cattle, the following color distribution was noted: 36% red (RR), 48% roan (Rr), and 16% (rr). Is this population in a Hardy-Weinberg equilibrium? Answer: Yes 10. List 4 factors that change gene frequencies in populations. Answer: mutation, migration, selection, genetic drift

11. Assume that in a Hardy-Weinberg population, 9% of the individuals are of the homozygous recessive phenotype. What percentage of the individuals would be expected to be heterozygous? What percentage homozygous dominant? Answer: 42% heterozygous, 49% homozygous dominant 12. A classic example of selection in natural populations involves the peppered moth Biston betularia, in England. Industrial gases killed the lichens and mosses on buildings, trees, etc., and soot deposited on the landscape. Dark-colored moths gained a selective advantage. In this case, one would say that there was selection against the light-colored moths. Which morph, light or dark, would have the highest fitness? Answer: the dark morph 13. In a population of 10,000 individuals, where 3600 are MM, 1600 are NN, and 4800 are MN, what are the frequencies of the M alleles and N alleles? Answer: M = .6; N = .4 14. What does the expression 2pq represent? Answer: the frequency of heterozygotes 15. Assuming that p = .3 for a population, what would be the expected frequency of heterozygotes for the involved allelic pair? Answer: 0.42 16. A certain form of color blindness in humans is sex-linked. Assume that 8 percent of the males in a population are color blind. What percentage of the females in this population are expected to be color blind? Answer: 0.64% 17. What is the original source of genetic variation in a population? Answer: Mutation 18. Mutation and migration introduce new alleles into populations. What is the principal force that shifts allelic frequencies within large populations? Answer: natural selection 19. What term is given to the probability that a particular phenotype will survive and leave offspring? Answer: fitness

20. The difference between fitness of a given genotype and another genotype considered as optimal is called the selection coefficient (s). What is the selection coefficient for a genotype (aa) when 99 of every 100 organisms successfully reproduce? Answer: s = 0.01 21. Which is more significant in changing gene frequencies, selection against a dominant gene or selection against a recessive gene? Answer: selection against a dominant gene 22. How is the degree of populational homozygosity related to the degree of inbreeding? Answer: Inbreeding increases homozygosity. 23. In extreme cases, genetic drift may lead to the chance fixation of one allele. What happens to other alleles of that gene? Answer: They are excluded or lost. 24. What is the term given to a measure of the loss of fitness caused by inbreeding? Answer: inbreeding depression 25. Which of the following is NOT an assumption of the Hardy-Weinberg Law? A. No mutation B. No selection C. Small population size D. Random mating E. No migration Answer: C 26. In a population with 4 AA, 2 Aa, and 2 aa individuals, what is the frequency of the a gene? A. 0.5 B. 1/8 C. 3/8 D. 0.25 E. None of the above Answer: C

27. In a population of 200 individuals where the frequency of the a gene is 0.4, according to the Hardy-Weingberg Law, what is the expected NUMBER of heterozygous individuals? A. 96 B. 100 C. 48 D. 72 E. None of the above Answer: A 28. With selection against the recessive genotype (aa), it takes more generations to reduce the frequency of the recessive gene (q) from 0.1 to 0.01 than it does from 0.5 to 0.1 because: A. At lower gene frequencies, more of the recessive alleles are in the homozygotes. B. At lower gene frequencies, more of the recessive alleles are in the heterozygotes. C. Random mating does not always occur at lower gene frequencies. D. All of the above. E. None of the above. Answer: B 29. With complete selection against recessive individuals (aa), what is the expected frequency of the a allele at equilibrium? ______________ Answer: 0 30. When Hardy-Weinberg equilibrium is reached: A. Gene frequencies change each generation. B. Genetic variability is maintained. C. Selection occurs against the recessives. D. One allele is fixed, another is lost. E. None of the above. Answer: E 31. The Δ32 allele: A. Is higher in frequency in northern compared to southern parts of Europe. B. May have been selected for because of bubonic plaque. C. Is due to a 32 base pair deletion.

D. All of the above. E. None of the above. Answer: D 32. The amount of change in gene frequency due to gene flow depends on the difference in gene frequency between migrants and natives, and ________________ Answer: proportion of migrants 33. Suppose we have three genotypes with the following fitnesses: +/+ 0.5, +/a 0.5, a/a 1. What is the expected equilibrium q value? ______________ Answer: 1...