what are the implications for the genetic structure of populations when the hardy–weinberg law is in effect? genotype frequencies are determined by allele frequencies. reproduction alone can bring about evolutionary change. when the two alleles in the population are equal, the frequency of homozygotes is maximized. a single generation of random mating produces the equilibrium frequencies of p2, 2pq, and q2. allele, but not genotype frequencies, can change over time.