Shaver Fitness Evolution

The paper “Fitness Evolution and the Rise of Mutator Alleles in Experimental Escherichia coli Populations,” by Aaron C. Shaver et al, discusses the evolution of mutation rates in terms of the fitness of the organism. Mutations in general are known to be beneficial in the long run but are harmful in the present time that it occurs. This is important to understand because it explains why the evolution of animals in such a long process, due to the deleterious nature of mutations, but when they do occur it and are sustained they are beneficial for the population for future generations. This paper specifically points out the statement by A.H. Sturtevant, that states, “The prevalence of deleterious mutations over beneficial mutations should evolve to the lowest value possible “given the nature of genes.”” This quote means that due to the deleterious nature of mutations, the evolution of genes over time will be a slow process; these changes will not be seen immediately within a population. In order to study this statement, the authors looked at the research completed by Snigegowski et al. which studied the indirect effect selection of deleterious and beneficial mutations have on the frequencies of alleles in the mutation

It showed that when the frequency of a mutator clone is intentionally increased above a threshold, the mutator will spread further in association with the new beneficial mutations. When the frequency is below the threshold, the mutator clone will usually decline in the frequency. This is because the wild type clone is more commonly associated with new beneficial mutations. Research has shown that mutator hitchhiking in natural bacterial populations is implied by the large amount of frequencies of mutator strains in some natural