What is a genetic drift?

Genetic drift is a fundamental concept in population genetics and evolutionary biology. It refers to the random fluctuations in the frequencies of alleles (different versions of a gene) within a population over generations. Genetic drift is a purely stochastic (random) process and can have significant effects on a population’s genetic makeup, especially in small populations.

Key points about genetic drift:

Random Process: Genetic drift occurs due to random chance rather than natural selection. It is not driven by any specific advantage or disadvantage associated with a particular allele.

Small Populations: Genetic drift is most pronounced in small populations because chance events can have a more significant impact on allele frequencies when there are fewer individuals.

Effects on Allele Frequencies: Over time, genetic drift can lead to the increase or decrease in the frequency of specific alleles in a population. Some alleles may become more common, while others may become less common or even be lost from the population entirely.

Loss of Genetic Diversity: Genetic drift tends to reduce genetic diversity within a population. Rare alleles are more likely to be lost through genetic drift, leading to a population that is less diverse in terms of its genetic makeup.

Founder Effect: Genetic drift can occur when a small group of individuals (founders) establishes a new population. The genetic makeup of the founder population may not accurately represent the genetic diversity of the original population, leading to a unique allele frequency pattern in the new population.

Bottleneck Effect: A bottleneck event, such as a natural disaster or human intervention, can drastically reduce the size of a population. The survivors of the bottleneck may have allele frequencies that differ from the original population, and this reduced genetic diversity can persist in subsequent generations.

Neutral Theory of Molecular Evolution: Genetic drift is a key concept in the neutral theory of molecular evolution, proposed by Motoo Kimura. According to this theory, many genetic changes at the molecular level are the result of genetic drift acting on neutral mutations, rather than natural selection.