Which term describes the fixation of alleles in a population?

The fixation of alleles in a population occurs when one allele of a particular gene becomes the only variant present in that population. This process is primarily driven by genetic drift, which refers to random fluctuations in allele frequencies from one generation to the next, particularly in small populations.

As random events occur, certain alleles may become more common simply due to chance, and over time, one allele may completely replace others, leading to its fixation. This process is distinct from natural selection, which involves differential survival and reproduction of genotypes based on their phenotypic traits, thereby favoring certain alleles over others due to their adaptive advantage in the environment. Genetic variation refers to the diversity of alleles and genotypes within a population, while a population bottleneck describes a sharp reduction in the size of a population due to environmental events, leading to a loss of genetic diversity.

Therefore, the correct answer is tied to the mechanism through which alleles can become fixed in a population over generations through random processes.