Question

What are the conditions under which Hardy-Weinberg equilibrium cannot be met?

Short answer

The five major conditions under which Hardy-Weinberg equilibrium can be disturbed are the presence of mutation, gene flow, non-random mating, genetic drift, and natural selection.

Step-by-step solution

No Mutation

In this step, remember that the Hardy-Weinberg equilibrium assumes no mutation occurs. Therefore, the first condition that, if broken, will disrupt this equilibrium is mutation. A mutation changes the allele frequencies in a population by introducing new alleles. Mutations contribute to genetic variability and can potentially shift the allele frequencies, breaking the Hardy-Weinberg equilibrium.

No Gene Flow

The second condition of the Hardy-Weinberg equilibrium is no gene flow. Gene flow refers to the movement of genes from one population to another through immigration or emigration. If gene flow occurs, the gene frequencies in a population may change, disrupting the equilibrium.

Random Mating

The third condition is Random Mating. The equilibrium assumes that individuals in a population mate randomly, meaning every individual has an equal chance of mating with every other. However, if there's non-random mating, some genes may be favored over others, which changes the overall allele frequency.

No Genetic Drift

The fourth condition is No Genetic Drift. Genetic drift refers to random changes in gene frequencies over time due to chance events. This is most significant in small populations and can lead to considerable shifts in allele frequencies over time, thus breaching the Hardy-Weinberg equilibrium.

No Natural Selection

The final condition is No Natural Selection. According to the Hardy-Weinberg equilibrium, no allele is favoured over another. If natural selection operates, certain traits will get selected over others, altering allele frequencies.