If the frequency of a homozygous dominant genotype is 0.49, what is the frequency of the homozygous recessive genotype?

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Answer 1 · 2016-05-23T12:20:44

0.09

You'll need to understand the Hardy-Weinberg equation, but you don't even need to use it to answer this question.

$p^{2} + 2 p q + q^{2}$ $p^2 + 2pq + q^2$ = 1

Let's re-write Hardy Weinberg using A and a.

$A^{2} + 2 A a + a^{2}$ $A^2 + 2Aa + a^2$ = 1

You also need to know that the frequencies of the two alleles will add to 1.

A + a = 1

If AA = 0.49

A = 0.7 (take the square root of 0.49)

Using this means a = 0.3 (1 - 0.7 = 0.3) Remember A + a = 1

So the frequency of aa = ${0.3}^{2}$ $0.3^2$ = 0.09