Genetic drift is the random change in the genetic composition of a population due to chance events causing unequal participation of individuals in producing succeeding generations. Along with natural selection, genetic drift is a principal force in evolution.

Allele Frequencies

Different forms of a gene are called alleles. Individual members of a population have different alleles. Together, all the alleles for all the genes in a population constitute the "gene pool" of the population. Through reproduction, individuals pass their genes on to the next generation. If considering only the effect of genetic drift, the larger the population is, the more stable the frequency of different alleles in the gene pool will be over time. In small populations allele frequencies are likely to change rapidly and dramatically over very few generations, or "drift," because of chance events. This rapid change can occur in small populations because each...