M-S Balance - Equations

The change in the frequency of the mutant allele in the next generation, due to selection, is calculated as:



where h is the degree of dominance.

Mutation, which occurs at a relatively constant rate, , acts to increase the frequency of the mutant allele in the population. Mutation rates are typically between and . The change in the frequency of the mutant allele in the next generation, due to mutation, is calculated as:



Because were talking about deleterious alleles here, selection invokes a negative change in q, whereas mutation invokes a positive change. When these two forces come into balance with each other, q comes to an equilibrium value (no change in q). When this is true, we can calculate the mutation rate for a particular allele given q,s, and h: