The Hardy-Weinberg Equilibrium can be expressed as an algebraic formula. Explain the usefulness of such an expression. How would the frequencies of two alleles be expressed; of three alleles?
The formula is useful in comparing the genotypic frequencies of one generation to another to determine if genetic equilibrium has been altered. For the consideration of the frequencies of two alleles, a binomial equation
where p equals the frequency of the dominant allele and q equals the frequency of the recessive allele, can be used to determine the genotypic ratios caused by the alleles. Thus, equals the frequency of the homozygous dominant genotype, 2pq equals the frequency of the heterozygous genotype, and equals the frequency of the homozygous recessive genotype. For each additional allele considered, another term must be added to the equation. For example, the consideration of the frequencies of three alleles requires the trinomial equation .
