Hardy-Weinberg Theorem

Question

When you apply the Hardy-Weinberg Theorem, what are you actually calculating?

How is this an example of a null model, and what is the alternate hypothesis that can be entertained only after demonstrating that the Hardy-Weinberg predictions are not supported by the actual numbers?

Answer 1

You are calculating the genotype frequencies of homozygous recessive, heterozygous, and homozygous dominant in a population. This is an example of a null model because we are assuming no outside factors are at play in the population: no mutation, random mating, no gene flow, infinite population size, and no selection. These are the assumptions that the Hardy-Weinberg model makes in order for the frequencies to be correct. An alternative hypothesis could be that the population is not at Hardy-Weinberg equilibrium for that gene as the frequencies are changing. This means that evolution is occurring!