Genetic drift is a mechanism of evolution characterized by random fluctuations in the frequency of a particular version of a gene (allele) in a population. Though it primarily affects small, isolated populations, the effects of genetic drift can be strong, sometimes causing traits to become overwhelmingly frequent or to disappear from a population.

Genetic Drift. Genetic drift is the change in frequency of an existing gene variant in the population due to random chance. Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. It could also cause initially rare alleles to become much more frequent, and even fixed.