Because they are diploid organisms, there are a total of 1000 copies of genes for flower color in the population of 500 individuals. Related to these allele frequencies are the frequencies of genotypes. Population geneticists use the term genetic structure to refer to a population s frequencies of alleles and genotypes. The genetic structure of a nonevolving population gene pool is described by the Hardy-Weinberg theorem. The Hardy-Weinberg theorem states that the frequencies of alleles and genotypes in a population s gene pool remain constant over the generations unless acted upon by agents other than sexual recombination.
Sexual recombination is the sexual shuffling of alleles due to meiosis.
Random fertilization has no effect on the overall genetic structure of a population. Every time a gamete is drawn from the pool at random, the chance that the gamete will bear an A allele is 0.8, and the chance that the gamete will have an a allele is 0.2. Using the Punnett square, we can calculate the frequencies of the three possible genotypes in the next generation of the population. Notice that the sexual processes of meiosis and random fertilization have maintained the same allele and genotype frequencies that existed in the previous generation of the wildflower population.