You discover a population of mustard plants and find it to be at Hardy-Weinberg equilibrium with respect to the R locus.Suppose there are two alleles at this locus and the frequency of one of those alleles (the r-6 allele) is 0.2.Of the individuals that carry at least one r-6 allele, what fraction will be heterozygotes?
A) 1/9
B) 1/5
C) 1/3
D) 4/5
E) 8/9

Question

Quizplus · Accepted Answer

In Hardy-Weinberg equilibrium, the frequency of heterozygotes (2pq) can be calculated using allele frequencies. If the frequency of the r-6 allele (q) is 0.2, then the frequency of the other allele (p) is 0.8. The frequency of heterozygotes is 2pq = 2(0.8)(0.2) = 0.32. The frequency of individuals carrying at least one r-6 allele is 1 - p^2 = 1 - (0.8)^2 = 0.36. The fraction of heterozygotes among those carrying at least one r-6 allele is 0.32 / 0.36 = 8/9.

You Discover a Population of Mustard Plants and Find It