If after studying a population for a trait determined by a single pair of alleles you fi nd that the population is not in equilibrium, what possible reasons might explain the lack of equilibrium

Answer and Explanation:

The criteria for maintaining a Hardy-Weinberg equilibrium are:  

Random matings: mating probabilities between individuals with determined genotypes depends on the products of frequencies of those genotypes. No superposed generations: each individual can leave their gametes in the pool only once.  No mutations: There is no incorporation into the genetic pool of new gametes originated by mutation of preexistent alleles. No migration: There is no incorporation of gametes originated in another population.    Infinite population size: the probabilities of randomly taking an A gamete from the pool are p and the probabilities of taking a B gamete from the pool are q.  No natural selection: Each individual has the same surviving and reproducing probabilities as any other, contributing proportionally to the gamete pool.  

If one of these points does not carry out, then the population under study is not in equilibrium.

If endogamy or exogamy occurs affecting random mating, If genetic drift is going on, the population is not infinite-sized and there are no random matings,If there exist genetic flux, which means that the population is not closed and migration occurs, If natural selection is acting over the population, If there occur mutations,

Then the observed allelic and genotypic frequencies are different from the expected ones if the population under study was in H-W equilibrium.