The frequency of the genotype aa in a population is 0.09. What is the frequency of the allele a in the population?
A)0.7
B)0.81
C)0.3
D)0.0081

Question

Quizplus · Accepted Answer

Let's assume p is the frequency of the dominant allele (A) and q is the frequency of the recessive allele (a). We know that aa genotype is present in the population at a frequency of 0.09. This means q^2=0.09. 
q^2 represents the frequency of the homozygous recessive genotype (aa), so we can calculate the frequency of the recessive allele (q) by taking the square root of q^2: 
q=sqrt(0.09)=0.3 
Now, we can calculate the frequency of the dominant allele (p) by subtracting q from 1: 
p=1-0.3=0.7 
Therefore, the frequency of the allele a in the population is 0.3 (option C).

The Frequency of the Genotype Aa in a Population Is