Which factor does not affect Hardy-Weinberg equilibrium?

The correct answer is Option (3) → Random Mating

Option (1) Gene migration — Affects Hardy-Weinberg equilibrium. Alleles move in or out with migrants.

Option (2) Genetic drift — Affects Hardy-Weinberg equilibrium. Allele frequencies change by chance.

Option (3) Random Mating — Does not affect Hardy-Weinberg equilibrium. Random mating is a condition for the equilibrium to hold.

Option (4) Mutation — Affects Hardy-Weinberg equilibrium. New alleles arise.

NCERT Extract:
Hardy-Weinberg Principle – “… Five factors are known to affect Hardy-Weinberg equilibrium. These are gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection. When migration of a section of population to another place and population occurs, gene frequencies change in the original as well as in the new population. New genes/alleles are added to the new population and these are lost from the old population.”