How can Hardy-Weinberg equilibrium be affected? Explain giving three reasons.

Hardy-Weinberg equilibrium affected by following reasons:

(i) Genetic drift – also known as Sewall Wright Effect. When a small group of organisms is separated from a large population, and this small group may not have all the alleles, i.e., they differ from the population from which it is separated in terms of certain genes. These random changes in the frequency of alleles affect the Hardy-Weinberg equilibrium.

(ii) Genetic Migration - When a small group of population is migrated to another place, gene frequencies change in the original as well as the new population. New genes/alleles are added to the new population, and these are lost from the population.

(iii) Mutation - These are very harmful. They occur randomly and at very slow rates. Mutations are generally the raw materials for evolution; they help in producing variations with genetic recombination. Mutations enrich the gene pool with new modified genes. A large scale accumulation of such genes will lead to evolutionary modifications.

(iv) Genetic recombination – New combination of genes occur due to crossing over meiosis, during gametogenesis.

(v) Natural selection – This occurs due to the inheritance of variations leading to change in allele frequency and support the survival of the fittest.