The equation p2 + 2pq + q2 = 1 is a binomial expansion of (p+q)2. It mathematically represents the Hardy-Weinberg’s principle which is used to calculate the genetic variation of a population at equilibrium. This principle states that “Allele frequencies in a population are stable and remain constant from generation to generation”.  Here, p represents the frequency of allele A, q represents the frequency of allele a, p2 represents the frequency of AA (homozygous) individuals in a population, q2 represents the frequency of aa (homozygous) individuals and 2pq represents the frequency of Aa (heterozygous) individuals Also, the sum of all the allelic frequencies is equal to 1. If p and q are known values, then the frequencies of the three genotypes can be calculated using the Hardy-Weinberg equation.