I. Quantifying Genetic Variation A. Genetic makeup 1. Example B. Changes in genetic makeup 1. We have defined Evolution as a change in gene frequency at one or more loci in a population, and have seen that this correspond to our intuitive notion of evolution as a change in the genetic composition of a population over time. Mutation as a cause of evolutionary change. A. Mutation is a very weak evolutionary force 1.
Mutation can cause change in gene frequencies directly.
For example, in a population that is fixed for allele A , and hence the frequency of that allele is 1.0, a mutation introductin allele a automatically reduces the frequency of A below 1.0. Additional mutations reduce the gene frequency even further. However, typical mutation rates are on the order of 1 mutation per gene per 10 -5 meiotic events. B. Nevertheless, mutation is crucial for the evolutionary process because it introduces genetic variation on which other processes can act to cause evolutionary change. A large majority of organisms in the world exhibit sexual reproduction, and thus carry on some sort of mating process.