The frequencies of genotypes at a locus resulting from random mating at that locus; for two alleles, A₁ and A₂, with respective frequencies p and q, the Hardy-Weinberg equilibrium frequencies are p² A₁A₁, 2pq A₁A₂, q² A₂A₂. Despite the simplifying assumptions required to predict these frequencies, most loci in most populations are in Hardy-Weinberg equilibrium. Thus the Hardy-Weinberg law, which predicts these frequencies, is one of the great unifying themes of biology.