Question

p² + 2pq + q² = 1. Explain this algebraic equation on the basis of Hardy Weinberg’s principle.

Answer 1

In a diploid if p represents the frequency of allele A and q represents the allele frequency of a, then frequency of AA individuals in a population is p² . Similarly of aa is q² and of Aa is 2pq. Hence p² + 2pq + q² = 1. This is a binomial expansion of (p + q)² . 

According to Hardy–Weinberg principle, total genes and their alleles in a population or gene pool remains constant. This is called genetic equilibrium. Sum total of all the allelic frequencies is 1 [p + q = 1/(p + q)² = 1].