homework 12
12.01 Consider a gene with two possible alleles, A1 and A2. Shown below are the numbers of the three genotypes in three different populations:
12.01 Consider a gene with two possible alleles, A1 and A2. Shown below are the numbers of the three genotypes in three different populations:
(a) Calculate the frequency of alleles A1 and A2 for each of the three populations.
(a) Calculate the frequency of alleles A1 and A2 for each of the three populations.
(b) What are the Hardy-Weinberg frequencies and expected genotypic numbers for the three populations?
(b) What are the Hardy-Weinberg frequencies and expected genotypic numbers for the three populations?
(c) Calculate the chi-square values for these populations. Are these populations statistically different from Hardy-Weinberg proportions?
(c) Calculate the chi-square values for these populations. Are these populations statistically different from Hardy-Weinberg proportions?
12.02 In a certain population, a gene under consideration has two alleles R and r. R is dominant to r. The frequency of R is 0.24. Assume that the genotype are in the Hardy-Weinberg proportions.
12.02 In a certain population, a gene under consideration has two alleles R and r. R is dominant to r. The frequency of R is 0.24. Assume that the genotype are in the Hardy-Weinberg proportions.
(a) Calculate the frequency of each genotype?
(a) Calculate the frequency of each genotype?
(b) What is the most common phenotype? What is least common phenotype?
(b) What is the most common phenotype? What is least common phenotype?
12.03 For a certain gene, A is dominant to a. In a population of 400 individuals, only 4 have the recessive phenotype; the rest are dominant.
12.03 For a certain gene, A is dominant to a. In a population of 400 individuals, only 4 have the recessive phenotype; the rest are dominant.
(a) What are the estimated frequencies of A and a?
(a) What are the estimated frequencies of A and a?
(b) What proportion of the population would you expect to be heterozygous?
(b) What proportion of the population would you expect to be heterozygous?
(c) What assumptions have you made in answering a and b?
(c) What assumptions have you made in answering a and b?
12.04 In an average human population, approximately 8% of the males are colorblind. Remember that this is an X-linked recessive trait. Assuming Hardy-Weinberg proportions, answer the following:
12.04 In an average human population, approximately 8% of the males are colorblind. Remember that this is an X-linked recessive trait. Assuming Hardy-Weinberg proportions, answer the following:
(a) What proportion of females would you expect to be color blind?
(a) What proportion of females would you expect to be color blind?
(b) What proportion of females would you expect to be carriers of the recessive allele (heterozygous)?
(b) What proportion of females would you expect to be carriers of the recessive allele (heterozygous)?
12.05 For a certain gene in a particular population, the initial genotype frequencies for are 0.04, 0.32, and 0.64 for the genotypes A1A1, A1A2, and A2A2 respectively. What is the frequency of heterozygotes after each generation of self-fertilization? Calculate the proportions for five generations.
12.05 For a certain gene in a particular population, the initial genotype frequencies for are 0.04, 0.32, and 0.64 for the genotypes A1A1, A1A2, and A2A2 respectively. What is the frequency of heterozygotes after each generation of self-fertilization? Calculate the proportions for five generations.
12.06 Explain why the genetic variation in small populations is usually lower that in larger populations? Why are genes more likely to become "fixed" in small populations?
12.06 Explain why the genetic variation in small populations is usually lower that in larger populations? Why are genes more likely to become "fixed" in small populations?
12.07 Compare, in general, the expected change in allelic frequencies that result from mutation, gene flow, genetic drift, and selection.
12.07 Compare, in general, the expected change in allelic frequencies that result from mutation, gene flow, genetic drift, and selection.
(a) Which factors will have the largest effect on allele frequencies, and when?
(a) Which factors will have the largest effect on allele frequencies, and when?
(b) How is the effect of genetic drift on allelic frequency different from that of selection?
(b) How is the effect of genetic drift on allelic frequency different from that of selection?