Passage VI

A student performed 4 computer simulation studies to model the change at a gene in a population. For each study, the following rules applied:

• The gene has 2 alleles (possible forms): A and a.

• Each organism has 2 copies of the gene.

• Thus, there are 3 possible genotypes (allele combinations for the gene): AA_, Aa, and aa.

• Different genotypes may have different fitnesses (the relative number of alleles per individual a genotype contributes to the next generation).

• The fitnesses of Genotypes AA, Aa, and aa are represented by W(AA), W(Aa), and W(aa), respectively.

• p = the proportion of the alleles that are in Form A.

• Changes in p are due to differences in the fitnesses of the genotypes.

• Time is measured in generations.

Study 1

Three simulations were done. In each, W(AA) = W(Aa) > W(aa), and the initial p = 0.1. See Figure 1.

Study 2

Three simulations were done. In each, W(AA) = W(Aa) < W(aa), and the initial p = 0.9. See Figure 2.

Study 3

Five simulations were performed. In each, W(AA) = 0.8; W(Aa)= 1.0; and W(aa) = 0.6, and the initial p varied. See Figure 3.

Study 4

Five simulations were performed. In each, W(AA) = 0.625; W(Aa)= 0.5; and W(aa) = 1.0, and the initial p varied. See Figure 4.