Imagine that you have two neighboring populations (1 and 2) of a species. There
ID: 56957 • 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.
Population 1: frequency of “A” p = 0.8
Population 1: frequency of “A” p = 0.2
Mixed population having half individuals from population 1 and rest half from population 2
Allele “A” p = 0.5
Allele “A” q = 0.5
Assuming that no mating has occured in the mixed population, the alleleic frequency can be calculated from the genotypic frequecny, but we cannot do the reverse unless we know the population size.
b. The mixed populationis no tin Hardy-Weinberg equilibrium.. This is due to the presence of sub-populations with different allele frequencies at a locus.
c. Due to the presence of isolated sub-populations, reduction is observed in the heterozygosity with different allelic frequencies, which do not interbreed as as single randomly mating unit. When, all the isolated sub-populations have the same gene frequencies, no variance among the subpopulation exists and no Wahlund effect occurs.