What is genetic drift?

Genetic drift is described as a mechanism of evolution that involves random fluctuations in the frequencies of alleles (different versions of a gene) within a population over time. This phenomenon occurs due to chance events that can cause certain alleles to become more or less common regardless of their importance to the organism's survival or reproduction.

For example, in a small population, an allele can increase in frequency simply by chance, especially if individuals carrying that allele reproduce more than others, or conversely, it can disappear entirely if individuals with that allele do not reproduce. This random sampling effect has a more pronounced impact in smaller populations, where the effects of genetic drift can lead to significant changes in genetic composition, ultimately influencing evolutionary trajectories.

Other options, while relevant to genetics and evolution, do not accurately define genetic drift. Selective breeding is a process actively chosen by breeders, rather than random. The extinction of species involves broader ecological and environmental factors and is not specifically linked to genetic drift. Genetic mutations caused by environmental factors refer to specific changes in the DNA sequence, rather than random changes in allele frequencies associated with drift.