A sampled “a” population has 36% of homozygous recessive genotype (aa). Then the frequency of allele “a” is

The correct option is 60%.

To find the frequency of the recessive allele "a", we can apply the Hardy-Weinberg principle. According to this principle, the frequencies of genotypes in a population in genetic equilibrium are represented by the equation:
$p^2+2pq+q^2=1$
where:
- $p^2$ represents the frequency of the homozygous dominant genotype (AA),
- $2pq$ represents the frequency of the heterozygous genotype (Aa), and
- $q^2$ represents the frequency of the homozygous recessive genotype (aa).
- $p$ is the frequency of the dominant allele "A", and
- $q$ is the frequency of the recessive allele "a".

We are given that the homozygous recessive genotype (aa) frequency is 36%. In decimal form, this is:
$q^2=0.36$

To find the frequency of the allele "a" (which is $q$), we take the square root of the homozygous recessive genotype frequency:
$q=\sqrt{0.36}$
$q=0.6$

Converting the decimal frequency back into a percentage:
$0.6\times 100=60\%$

Therefore, the frequency of the allele "a" is 60%.