Question

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?A) 0.49B) 0.7C) 0.42D) 0.21

Answer 1

The correct answer is C)0.42

When there is Hardy-Weinberg equilibrium like in this case of a single locus with two alleles denoted A1 and A2 with frequencies f(A1) = p and f(A2) = q, the expected genotype frequencies under random mating are f(A1A1) = p² for the A1A1 homozygotes, f(A2A2) = q² for the A2A2 homozygotes, and f(A1A2) = 2pq for the heterozygotes. We have:

p+q= 1 q=1-p

Frequency of allele A1 is 70%=0.7 p=0.7

Frequency of allele A2 is q=1-0.7=0.3

Flies that carry both A1 and A2 alleles are heterozygotes (2pq)

Proportion is 2*0.7*0.3=0.42