The Natural Selection Model I: dominant allele favored. The final allele frequency was always different, though sometimes higher and sometimes lower than at the start.Ĭ. The model was run five times, always starting with the same allele frequency. The result : allele frequencies change randomly (and unpredictably) over time. In Population C the allele frequencies change from 50% A and 50% a to 100% A, while in Population D there is almost no change in frequencies. An aa individual in each population dies. Population C has two individuals while Population D has 5000.
Consider two populations, each with 50% genotype AA and 50% aa. It most strongly effects small populations. Genetic drift is change in allele frequencies due to random events. The frequency of the dominant allele in a small population (less than 100 individuals) is graphed over 100 generations. The genotypes of the individuals in the populations are different, but the allele frequencies are the same in both populations: 50% A and 50% a. For example, consider two small populations, each with two individuals. This does not mean that genotype frequencies can't change over time. The model was run five times (see the different colored lines) and each time, the allele frequency at the first generation equals the allele frequency at the last generation. The result : there is no change in allele frequencies over time. The following rules are in effect: the population is large, there is no migration of individuals, mating is random, there is no natural selection, and no mutation. The frequency of the dominant allele (A) in a population is graphed over 100 generations.
Below is a review of the various population genetics models covered in lab.