Factors affecting allele frequency. Coefficient of inbreeding. Coefficient of consanguinity.
Allele frequencies within a population are not fixed. They shift over time due to evolutionary forces that disrupt Hardy–Weinberg equilibrium. When these forces act on a population, they alter how common certain alleles are across generations, which is the foundation of evolutionary change. The major forces discussed here include mutations, migration (gene flow), and natural selection.
Mutations
Mutations are changes in DNA that convert one allele into another and are the ultimate source of all new genetic variation. Although individual mutation events are relatively rare, they occur in every generation across all organisms. Most mutations are neutral or harmful, while beneficial mutations are rare but impactful because they may increase in frequency if favored by natural selection. Mutation rates vary widely between organisms and even between different genes within the same genome. Environmental factors and disturbances in DNA repair can further raise mutation rates. While mutations
introduce essential raw material for evolution, the accumulation of harmful mutations can lead to genetic disorders or developmental abnormalities. Small populations are more vulnerable to the effects of mutations due to reduced buffering capacity. A harmful allele can remain at low frequencies in a population if continually reintroduced by mutation, even when being selected against.