CBSE Class 10 Answered

Genetic drift is an overall shift of allele distribution in an isolated population, due to random fluctuations in the frequencies of individual alleles of the genes. The concept was first introduced by Sewall Wright in the 1920s.

The process of change in the gene frequencies of a population due to chance events. The individual changes are most often small or gradual and the genetic drift is most often slow. But in the long run it can constitute a large part of the changes in a gene pool. Genetic drift also often cause alleles to disappear completely.

Genetic drift is a kind of complement to natural selection. While natural selection is a non-random process which makes alleles more or less widespread in a population over time due to the their effects on survival and reproductive success, genetic drift are those changes that have not such phenotypic causes

Genetic drift depends strongly on small population size since the law of large numbers predicts weak effects of random sampling with large populations. Genetic drift has no preferred direction, but there is a tendency within small populations towards homozygosity of a particular allele, such that over time the allele will either disappear or become universal throughout the population. genetic drift operates randomly while natural selection functions non-randomly. This is because natural selection emblematizes the ecological interaction of a population whereas drift is regarded as a sampling procedure across successive generations without regard to fitness pressures as dictated by the environment. Drift affects genotypic frequencies within a population whereas natural selection concerns itself both with both the phenotypes and genotypes present in a population