Dynamics without selection

Consider a diploid population with two alleles (A and a).

Relative fitnesses of AA, Aa, and aa all equal one. Let

x+y+z=1. Why?

Case 1: Individuals produce haploid gametes that form a gamete pool.

The frequency of allele A in the gamete pool will be? p =

The frequency of allele a in the gamete pool will be? q =

Gametes unite at random in the gamete pool to produce diploid offspring. To calculate the offspring frequency we use mating tables.

Gamete Mating Table

These are known as the Hardy-Weinberg frequencies.

Point 1: Populations not at Hardy-Weinberg reach Hardy-Weinberg equilibrium after only one generation of random mating (as in the above example). Caveat: Generations must be discrete.

The frequency of allele A in the next gamete pool will be? p' =

The frequency of allele a in the next gamete pool will be? q' =

Point 2: In the absence of selection and mutation, allele frequencies stay constant. Segregation does not change allele frequencies.