If the allele frequency of the HbS allele is 0.3 in a population, what is the frequency of the HbA allele (assuming this is a two-allele system) ?

0.7

Explanation:

In solving Hardy Weinberg related question; we use the formula:

p + q = 1 and/or

p² + 2pq + q² = 1

where:

p = frequency of the dominant allele

q = frequency of the recessive allele

p² = frequency of individuals with the homozygous dominant genotype

2pq = frequency of individuals with the heterozygous genotype

q² = frequency of individuals with the homozygous recessive genotype.

So, if p + q = 1

and allele frequency of HbS = 0.3;

Let the frequency of allele of HbS be (q) = 0.3 (since HbS is a recessive sickle cell traits)

Let the frequency of allele of HbA be (p) = ? (since HbA is a normal hemoglobin)

Then; to determine the allele of HbA; we have

p+q = 1

p + 0.3 = 1

p = 1 - 0.3

p = 0.7

∴ the frequency of the HbA allele = 0.7