PRACTICE POPULATION
GENETICS PROBLEMS
1. Penguins from Antarctica migrate to New Zealand at a rate of about 0.005 penguins per year (there are no known cases of migration in the opposite direction). Antarctic penguins carry an allele, x, that is relatively rare in New Zealand (its frequency in New Zealand is only 0.01) but common at the pole (its frequency there is 0.25). In New Zealand there is strong selection against this allele (s = 0.8). What will be the equilibrium frequency of the x allele in New Zealand?
2. "Dullard" is a homozygous recessive condition. 40 people in a 1000 are dullards. Determine the frequency of the dullard allele. Dullards produce 80 offspring for every 100 produced by non-Dullards. The dominant non-Dullard allele mutates to the dullard allele at a rate of 0.005. Given this scenario, what will be the equilibrial frequency of the dullard allele?
3. Suppose you have a population of 200 black-tailed prairie dogs. Assume that half the population is male and half female, but that only 30 males will mate in a given year with the females (all the females reproduce). What is the effective population size for these animals?
4. Assume these 3 genotypes: BB Bb bb. What would the frequencies of each genotype be after 5 generations of assortative mating?
5. (a) Suppose that the heritability of horn size in rhinos is 0.75. In a sample of rhinos from Namibia, average horn size in males was 47 cm, but males with horns exceeding 50 cm had the highest fitness. What will be the average horn size of males in the next generation? (b) Suppose we don’t know the heritability of horn size in rhinos, but, given the population in part (a), we document that average horn length was 48.2 cm in the following generation. If so, what is the heritability of horn size in this population?
6. (a) In capybaras there is a lethal mutant called "stone" which causes its bearers to drown at birth (capybaras are aquatic rodents). In a population of 100 capybaras, 9 were stone individuals. How many generations would it take to reduce the frequency of the stone allele to 0.01? (b) Suppose that stone is not lethal, but has a fitness of 0.6 compared with the dominant, non-stone allele. Calculate how much the stone allele will change in frequency in the next generation under these conditions.
7. Suppose for a moment that the propensity to attend VSU is a recessive trait (the so-called "Blazer" gene), (b), with "non-Blazerness" (B) being dominant. In a population of 1000 individuals, suppose we find that 60 attend VSU. Calculate the frequency of the Blazer and non-Blazer alleles in this population and the frequencies of each genotype. Now, assume that, using genetic screening, we find that the actual number of individuals with each genotype is as follows: 75-Blazers, 275-heterozygotes, 650-homozygote non-Blazers. (a) Is this population in Hardy-Weinberg equilibrium? Why or why not? (b) Calculate the fitnesses and selection coefficients of each genotype in this population. (c) Assume Blazers mate only among themselves and non-Blazers among themselves. What would be the frequencies of the three gentoypes after 5 generations of this kind of mating?
8. In a population of southern right whales, fluke patterns are influenced by 3 genotypes (FF, Ff, and ff). Sampling of a population near Argentina found 130 FF, 410 Ff and 460 ff individuals. (a) Determine allele frequencies in this population and whether or not it is in Hardy-Weinberg equilibrium. (b) Calculate the fitness and selection coefficients for each genotype. (c) Assume that the selection coefficient for the homozygous recessive genotype represents the strength of selection on the recessive allele. What will be the frequency of this allele in the next generation?