Topics in Genetics & Evolution KV 320.080 WS 2015 Homework quantitative genetics (Lecture 4):

Question 1: Suppose that a random sample of 400 snapdragons from a population includes 185 red, 150 pink, and 65 white. Estimate the allele frequency p of I and q of i. Assuming random combinations of alleles in the genotypes, what are the expected numbers of the three genotypes? Do the observed data seem to fit the Hardy-Weinberg expectations?

Question 2: Phenylketonuria is an autosomal recessive form of severe mental retardation. About one in 10,000 newborn Caucasians are affected. Assuming random mating, what is the frequency of heterozygous carriers?

Question 3: A species of butterflies occurs in two distinct morphs, A and B. You sample two areas and count 26 A and 28 B butterflies in one area, and 10 A and 21 B in another area. Is it possible that these two samples could come from a single homogeneous population, or are the frequencies of the two morphs significantly different from one another?

Question 4. Industrial melanism refers to the evolution of black (melanic) color patterns in several species of moths that accompanied progressive pollution of the environment by coal soot during the industrial revolution. The various color forms of the moths are known as morphs. The evolution of melanism has been observed in Great Britain, West Germany, Eastern Europe, the United States, and in other heavily industrialized areas. The species that evolve melanism are typically large moths that fly by night and rest in a sort of cataleptic state by day, often on the trunks of trees, using their cryptic black and- white mottled color pattern for concealment from visually cued predators such as hedge sparrows, redstarts, and robins. Of nearly 800 species of large moths in the British Isles, where industrial melanism has been most intensively studied, about 100 species are industrial melanics (Bishop and Cook 1975). The best known of these are the peppered moth (Biston betularia) and the scalloped hazel moth (Gonodontis bidentata). In most instances, the melanic color pattern has been found to be due to a single dominant allele. In one study of a heavily polluted area near Birmingham, England, Kettlewell (1956) observed a frequency of 87% melanic Biston betularia. Estimate the frequency of the dominant allele leading to melanism in this population and the frequency of melanics that are heterozygous.

Question 5. The ABO blood groups are controlled by three alleles designated I0, IA, and IB. Genotypes IAIA and IAIO have blood type A; genotypes IBIB and IBI0 have blood type B, genotype I0I0 has blood type 0, and genotype IAIB has blood type AB. In a sample of 1617 Spanish Basques, the numbers of A, B, 0, and AB blood types observed were 724, 110, 763, and 20, respectively (Mourant et al. 1976). The best estimates of allele frequency are p1 = 0.2661 (for IA), p2 = 0.0411 (for IB), and p3 = 0.6928 (for IO). Calculate the expected numbers of the four phenotypes and carry out a chi-square test for goodness of fit to the Hardy-Weinberg expectations.