Imagine that you have two neighboring populations (1 and 2) of a species. There
ID: 36229 • Letter: I
Question
Imagine that you have two neighboring populations (1 and 2) of a species. There is random mating within each population, so they are each in Hardy-Weinberg equilibrium for a locus with two alleles (A and a). In population 1, the frequency of the A allele is p = 0.8. In population 2, the frequency of the A allele is p = 0.2. Imagine that you generate a mixed population consisting of half individuals from population 1 and half individuals from population 2. [For parts (a), (b), and (d) below, you should show calculations that justify your answer, but you do not need to provide a written explanation.]
a. Assuming no mating or reproduction has yet occurred in the mixed population, what are the allele and genotype frequencies in the mixed population?
b. Is the mixed population in Hardy-Weinberg equilibrium? If not, is there an overrepresentation or underrepresentation of heterozygotes in the population relative to Hardy-Weinberg expectations?
c. For part (b), you should have found that the population is not in Hardy-Weinberg equilibrium. This is an illustration of what is known as the Wahlund Effect, in which an overall (mixed) population can deviate from Hardy-Weinberg equilibrium if there are isolated subpopulations with different allele frequencies (even if each individual subpopulation is in Hardy-Weinberg equilibrium itself).
Briefly explain why the presence of isolated subpopulations within a population can have similar effects on genotype frequencies as inbreeding among close relatives within a population.
d. Now imagine that the mixed population that you generated starts undergoing random mating. How many generations should it take for genotype frequencies to return to Hardy-Weinberg expectations?
Explanation / Answer
Answer:
a) So, let me illustrate with two hypothetical populations:
A1A1 A1A2 A2A2
Population 1 50 0 50
Population 2 25 50 25
At each locus I