Q.A population will not exist in Hardy-Weinberg equilibrium if :

Non-random (selective) mating is one of the classic factors that disrupts Hardy-Weinberg equilibrium.

The Hardy-Weinberg principle predicts that allele and genotype frequencies in a population remain constant across generations only if several idealised conditions hold: a very large population size (to avoid genetic drift), no mutation, no migration (gene flow), no natural selection, and random mating. If individuals mate selectively -- choosing mates based on particular traits rather than at random -- genotype frequencies shift away from Hardy-Weinberg expectations even without any change in allele frequency itself. The other three options (a large po …