Question

What is genetic drift? What happens to the alleles under this process? Can it be called evolution? How is it different from natural selection? Answer these problems in 3-4 sentences. You must provide a real example related to a bottleneck effect.

Answer 1

Genetic drift is a mechanism of evolution like natural selection, mutation, and migration. It refers to the random changes in the frequency of the alleles over time in a population, i.e can either increase or decrease randomly. This is the major difference with Natural Selection because, NAtural selection is not random. Unlike genetic drift that can be beneficial or detrimental or ineffective, natural selection only favors selection of positive and beneficial adaptations only. This mostly occurs in a small population because the alleles tend to be fixed over time by mating between the few members of the species. In case it happens, an allele can be lost by genetic drift or may be fixed so that it is the only allele that is present in the population. So the important consequence of Genetic drift is the loss of variation, i.e the loss of heterozygosity in the population. In population bottlenecks, the population is drastically reduced due to a natural event such as the eruption of Toba supervolcano in Indonesia reducing the population to around 10,000-20,000 humans. The population that emerges after genetic drift has taken place is considerably different from the ancestral population and so it is said to be a mechanism of evolution.