Originally published as Genetics Published Articles Ahead of Print on August 22, 2005.

Genetics, Vol. 171, 2133-2138, December 2005, Copyright © 2005
doi:10.1534/genetics.105.046094

Persistence Time of Loss-of-Function Mutations at Nonessential Loci Affecting Eye Color in Drosophila melanogaster

Lev Y. Yampolsky*,1, Chenoa Allen*, Svetlana A. Shabalina{dagger} and Alexey S. Kondrashov{dagger}

* Department of Biological Sciences, East Tennessee State University, Johnson City, Tennessee 37614-1710 and {dagger} National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD 20894

1 Corresponding author: Department of Biological Sciences, East Tennessee State University, Johnson City, TN 37614-1710.
E-mail: yampolsk{at}etsu.edu

Persistence time of a mutant allele, the expected number of generations before its elimination from the population, can be estimated as the ratio of the number of segregating mutations per individual over the mutation rate per generation. We screened two natural populations of Drosophila melanogaster for mutations causing clear-cut eye phenotypes and detected 25 mutant alleles, falling into 19 complementation groups, in 1164 haploid genomes, which implies 0.021 eye mutations/genome. The de novo haploid mutation rate for the same set of loci was estimated as 2 x 10–4 in a 10-generation mutation-accumulation experiment. Thus, the average persistence time of all mutations causing clear-cut eye phenotypes is ~100 generations (95% confidence interval: 61–219). This estimate shows that the strength of selection against phenotypically drastic alleles of nonessential loci is close to that against recessive lethals. In both cases, deleterious alleles are apparently eliminated by selection against heterozygous individuals, which show no visible phenotypic differences from wild type.