If in either monoecious or dioecious organisms, either the allele or genotype proportions are initially unequal in either sex, it can be shown that constant proportions are obtained after one generation of random mating. If dioecious organisms are heterogametic and the gene locus is located on the X chromosome, it can be shown that if the allele frequencies are initially unequal in the two sexes ["e.g"., XX females and XY males, as in humans], in the heterogametic sex 'chases' in the homogametic sex of the previous generation, until an equilibrium is reached at the weighted average of the two initial frequencies.