# If the frequency of the p allele is .63 in the population then what is the frequency of the q allele?

Jun 3, 2018

$0.37$

#### Explanation:

We use the Hardy-Weinberg equation, which states that,

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

where:

• ${p}^{2}$is the frequency of the homozygous genotype $\text{AA}$

• $2 p q$ is the frequency of the heterozygous genotype $\text{Aa}$

• ${q}^{2}$ is the frequency of the homozygous genotype $\text{aa}$

• $p$ is the frequency of the dominant allele $\text{A}$

• $q$ is the frequency of the recessive allele $\text{a}$

Since we only need to find the frequency of the $q$ allele, we can factor the equation into:

${\left(p + q\right)}^{2} = 1$

Plugging in for $p = 0.63$, we get:

${\left(0.63 + q\right)}^{2} = 1$

$0.63 + q = 1$

$q = 1 - 0.63$

$= 0.37$