Mutations are errors in DNA synthesis that sometimes lead to new phenotypes in subsequent generations. Many of these new phenotypes are unsuitable for survival in an organism's environment, and thus the allele is gradually cleared from the population. Suppose you are studying such a trait in the laboratory- how would you go about calculating the frequency of such a deleterious allele?

Suppose there is a single locus with two alleles, A and a, with frequencies p and q = 1 - p, respectively. We will assume that allele a is deleterious and recessive, and that mutations only occur in a forward direction at a rate of μ per generation. If s is the selection coefficient corresponding to allele a, where s = 0 implies neutrality and s = 1 implies lethality, the equilibrium frequency of allele a (given by q*) is approximated as,

where 0 < s < 1. This equation is a power function. Could you use it in the classroom or laboratory? If not, then continue with this tutorial and try out the problems at the end of the section.

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In the next section we explore the basics of power functions.

The basics