Question

A gene locus has two alleles A and a. If the frequency of dominant allele A is 0.4, then what will be the frequency of homozygous dominant, heterozygous and homozygous recessive individuals in the population?

• A. 0.16 (AA); 0.36 (Aa); 0.48 (aa)
• B. 0.36 (AA); 0.48 (Aa); 0.16 (aa)
• C. 0.16 (AA); 0.24 (Aa); 0.36 (aa)
• D. 0.16 (AA); 0.48 (Aa); 0.36 (aa)

Answer 1

The correct option is D 0.16 (AA); 0.48 (Aa); 0.36 (aa)

Frequency of dominant allele (p) = 0.4
Applying Hardy Weinberg equilibrium:
p + q = 1
q = 1 - 0.4 = 0.6
$p^2+q^2+2\mathrm{pq}=1$
Frequency of homozygous dominant genotype, $p^{\mathrm{2\; (}}\mathrm{AA}$) = $0.4^2$= 0.16
Frequency of heterozygote, 2pq (Aa) = 2 × 0.4 × 0.6 = 0.48
Frequency of homozygous recessive genotype, $q^2$ (aa) = $0.6^2$ = 0.36