Genetic Drift

Genetic drift is the change in gene or allele frequency in a population due to chance events, not because one allele is inherently better adapted than another. It becomes more significant when the population is small or reproductively isolated.

1. Loss of alleles: Low-frequency alleles are especially likely to disappear from a small population by chance. This reduces genetic variation within that population.
2. Increase in homozygosity: As variation decreases, the proportion of heterozygotes declines, and homozygotes become more common, especially in small inbreeding populations.
3. Divergence from the parent population: A small isolated population may develop genetic characteristics different from those of the original population. Over time, this divergence can become significant.
4. Role in speciation: The note states that genetic drift can contribute to the origin of a new species, especially in isolated populations such as island populations.
5. Risk of extinction: Random genetic drift may also push a small population toward extinction if important alleles are lost or if the population becomes too genetically limited.

• Genetic drift is the random fluctuation of allele frequencies due to chance events rather than adaptive advantage.
• It exerts a profound impact on small or isolated populations, frequently causing the random loss of low-frequency alleles and reducing overall genetic variation.
• This reduction in genetic diversity directly leads to a decline in heterozygosity and a subsequent increase in homozygosity.
• Isolated populations subjected to genetic drift may diverge significantly from their parental populations, actively contributing to the formation of new species.
• The random elimination of essential alleles severely restricts genetic diversity, thereby increasing the risk of extinction for small populations.