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Suppose you have a population of flour beetles with 1,000 individuals.Normally the beetles are red;however,this population is polymorphic for a mutant autosomal body color,black,designated by bb.Red is dominant to black,so BB and Bb genotypes are red.Assume the population is at Hardy-Weinberg equilibrium,with equal frequencies of the two alleles.
-What would be the expected frequencies of the homozygous dominant,heterozygous,and homozygous recessive (in that order)after 100 generations,assuming that no selection or other evolutionary processes are operating?
A) 0.75;0.20;0.05
B) 0.25;0.5;0.25
C) 0.33;0.33;0.33
D) All red,because it is the natural color
E) All black,because all red alleles would mutate to black

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Quizplus · Accepted Answer

Since the population is at Hardy-Weinberg equilibrium, the expected frequencies of genotypes will remain the same over time. Using the Hardy-Weinberg equation, p^2 + 2pq + q^2 = 1 (where p = frequency of dominant allele, q = frequency of recessive allele, and p + q = 1), we can determine the expected frequencies of each genotype. For a population with equal frequencies of the two alleles, p = q = 0.5. Thus, the expected frequencies of the genotypes are: BB = p^2 = 0.25, Bb = 2pq = 0.5, and bb = q^2 = 0.25, which corresponds to choice B.

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