Question

In a population at Hardy Weinberg equilibrium, the allele frequency of ‘A’ is 0.3, the expected frequency of ‘Aa’ individuals is
A. 0.21
B. 0.42
C. 0.63
D. 0.18

Answer 1

A mathematical equation was given by Hardy Weinberg. It is a type of equation that can be used to calculate the genetic variation of a certain population at equilibrium. If allele frequencies are known then, the frequency of three genotypes can be calculated.

Complete answer: The Hardy Weinberg equation can be used to estimate the occurrences of alleles in a population.
The equation is as follows-
${p^2} + 2pq + {q^2} = 1$
In the above equation, where p is the frequency of the dominant allele and q represents the frequency of the recessive allele. According to the information provided in the question, p is represented by A, and q is represented by a. The three expressions indicate the frequencies of three genotypes-
${P^2} =$frequency of the homozygous dominant genotype AA
$2Pq =$frequency of heterozygous genotype Aa
${q^2} =$frequency of homozygous recessive genotype aa
Thus,
$\left( {p + q} \right) = 1$
$\left( {0.3 + q} \right) = 1$
$\;q = 1 - 03 = 0.7$
$Aa = 2 \times 0.3 \times 0.7 = 0.42$
Hence, the correct option is (B), i.e., 0.42

Note: Allele frequency is the number of occurrences of an allele in a population. It can be determined by using the Hardy Weinberg equation. It states that the genetic variation in a population remains constant from one generation to the next in the absence of some disturbing factors. It is a type of null model between genotypic frequencies and alleles. The population should not experience any mutation, random mating, etc.