Evidence for the Partial Dominance of Recessive Lethal Genes in Natural Populations of Drosophila

Abstract

An earlier study by Hiraizumi and Crow showed that recessive lethals extracted from nature decreased the viability of heterozygotes by about 2 to 3% when tested in the laboratory. In the present article we have used published data on mutation rates, frequency of lethal chromosomes, and proportion of allelism among lethal chromosomes from wild Drosophila populations in order to make an indirect estimate of what the effective dominance of lethals must be in nature. For D. melanogaster the mean value of h + F is .015 and for the other species is .018, where h is the average deleterious effect of a heterozygous lethal gene and F is a measure of non-random mating within a locality. Since F, we believe, is probably small, this analysis is regarded as further evidence for the conclusion that recessive lethals extracted from natural populations (and newly occurring lethal mutants, a fortiori) have a deleterious effect as heterozygotes.