Population genetics aims to understand the genetic structure of a population, and how this can change over time. Population genetics deals mainly with discontinuous variation at single loci.
Allele frequency is the fundamental measurement used to define population structure.
Allele frequency is calculated from genotype frequencies. Genotype frequencies depend on allele frequencies and the breeding pattern in the population. Frequencies of specific matings are determined by genotype frequencies and the breeding pattern in the population. The proportion of an allele found in heterozygotes is maximal when the allele is rare. Inbreeding shifts the equilibrium in favour of homozygotes.