Question

In a Hardy-Weinberg population with two alleles ( $A$ and $a$ ) that are in equilibrium the frequency of the allele $A$ is $0.2$, What is the percentage of the population that is heterozygous for this allele?
a. $0.32$
b. $4$
c. $16$
d. $32$

Answer 1

Hardy – Weinberg Principle mathematically explains the occurrence and consistency of gene frequency for a particular gene. The principle expresses that the allelic frequency endures constant through generations and the gene pool remains constant. This phenomenon is known as genetic equilibrium. Also, all the allelic frequencies summarize to $1$.

Complete answer:
As stated in the Hardy-Weinberg equation, the sum of or summarize allele frequencies for all the alleles at the locus should be $1$ , so $p + q = 1$ . Also, the Hardy-Weinberg equation is stated as: ${p^2} + 2pq + {q^2} = 1$ ;
Where $p$ is the frequency of the " $A$ " allele and $q$ is the frequency of the " $a$ " allele in the population.
In this equation, ${p^2}$ shows the frequency of the homozygous genotype $AA$ , ${q^2}$ shows the frequency of the homozygous genotype $aa$ , and $2pq$ shows the frequency of the heterozygous genotype $Aa$.
Here, $q = 0.2$ .Hence, $p = 1 - q = 1 - 0.2 = 0.8$
So now, population of heterozygous individual will be $2pq$ as raised that is $2 \times 0.8 \times 0.2 = 0.32$
It implies, there is $32\%$ of the heterozygous population.

Hence, the correct answer is option (D).

Additional information:
Some factors that affect the Hardy-Weinberg principle are listed below:
• Mutation
• Genetic drift
• Natural selection
• Genetic recombination
• Gene flow
All above factors contribute to the change in frequency of genes of a species in a locality. If a few individuals from a species migrate to a new place or another place, the gene frequency changes again. It reduces from the place from where the individuals migrate and increases in the place they migrate to.

Note: In the Hardy-Weinberg population, the percentage of the population that is heterozygous for these allele mechanisms contribute to the process of evolution. Evolution involves changes in the gene pool. A population in Hardy-Weinberg equilibrium shows no change.