You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 25%. Calculate the frequency of the "A" allele. *
1 point
0.5
0.4
0.25
0.6

.5

Explanation:

Remember that p = dominant allele, q = recessive allele. Use the Hardy-Weinberg equations:

p^2 + 2pq + q^2 = 1      (AA + Aa + aa = 1)

So aa = q^2. Take the square root, and we'll have just q by itself.

√a^2 = √.25 = .5

So the frequency of the a allele (recessive) = .5.

p + q = 1

p + .5 = 1

p = .5

The frequency of the A allele is .5.