Q.Explain how mutations, natural selection and genetic drift affect Hardy Weinberg equilibrium.

Step 1. Hardy–Weinberg equilibrium requires, among other conditions, no mutation, no natural selection and no genetic drift (effectively infinite population size).

Step 2. Mutation directly creates new alleles or converts one allele into another, adding or altering variation in the gene pool — even though the rate is usually low, this by definition changes p and q away from a fixed value.

Step 3. Natural selection makes certain genotypes more or less likely to survive and reproduce than others, so the allele carried by the favoured genotype increases in frequency across generations while the disfavoured allele declines.

Step 4. Genetic drift changes allele frequencies purely by chance in the sampling of which individuals happen to reproduce, and this effect is strongest in small populations (via the bottleneck or founder effect), again shifting p and q unpredictably from one generation to the next. …

Take each force in turn and show how it changes allele frequency, directly break …

• Describing only what each force does in general, without explicitly tying it back to violating a specific Hardy–Weinberg assumption. …