Question

Select the correct option with respect to the Hardy-Weinberg equation,
$p^2+2pq+q^2=1$

• A. $p^2$ represents the frequency of the individuals with two dominant alleles for a gene
• B. $q^2$ represents the frequency of the individuals with two dominant alleles for a gene
• C. 2pq represents the frequency of the individuals with two recessive alleles for a gene
• D. 2pq represents the frequency of the individuals with two dominant alleles for a gene

Answer 1

The correct option is A $p^2$ represents the frequency of the individuals with two dominant alleles for a gene

Hardy-Weinberg principle given by Hardy and Weinberg states that frequencies of alleles tend to remain constant from one generation to the next in sexually reproducing populations under certain conditions.

The Hardy-Weinberg equation is an algebraic equation which is an expression of the Hardy-Weinberg principle.

According to Hardy Weinberg equation, if there are two alleles for a particular gene where A represents the dominant allele and a represents the recessive allele, then the frequency of A is p and a is q.
Combined frequencies of all alleles for a gene in a population is equal 1.
Therefore, p+q=1.
The frequency of homozygous dominant individuals (AA) in the population would be equal to pxp or $p^2$
The frequency of homozygous recessive individuals (aa) in the population would be equal to qxq or $q^2$
Since there are two ways of forming the heterozygote Aa, (allele A from the father and a from mother and vice versa) the frequency of heterozygous dominant individuals (Aa) in the population would be 2pq.
The sum of all three genotypic frequencies is $p^2+2pq+q^2=1$ which is a binomial expansion of ${(p+q)}^2$

p = frequency of the dominant allele (A)
q = frequency of the recessive allele(a)
$p^2$ = frequency of homozygous dominant individuals (AA)
$q^2$ = frequency of homozygous recessive individuals (aa)
2pq = frequency of heterozygous dominant individuals (Aa)