Hardy-Weinberg Principle
According to the Hardy-Weinberg Principle, the genetic makeup of a population remains constant from one generation to the next assuming five things do or do not occur. Change in the population's genetic makeup will not occur if: individuals mate randomly; no mutations occur; there is not an unequal migration of alleles in or out of the population (no gene flow); there is no genetic drift; and there is no natural selection.
Below is an example that shows how random mating alone does not change the genetic makeup in a population. Some relationships to consider are the frequency of alleles and the frequency of genotypes. The frequency of alleles in a population is demonstrated by the equation "p + q = 1" where "p" is the frequency of the dominant allele and "q" is the frequency of the recessive allele. The frequency of genotypes in a population is demonstrated by the equation "p2 + 2pq + q2" where "p2" represents the frequency of homozygous dominant individuals, "2pq" represents the frequency of heterozygous individuals, and "q2" represents the frequency of homozygous recessive individuals.