deleterious mutation

Fry JD, Keightley PD, Heinsohn SL & Nuzhdin SV 1999 New estimates of the rates and effects of mildly deleterious mutation in Drosophila melanogaster. PNAS 96:574-579.

• the most detailed information comes from the work of Mukai and Ohnishi
• who allowed mutations to accumulate on Drosophila melanogaster second chromosomes
• averaged over studies, the estimated rate of nonlethal viability mutations per second chromosome per generation under an equal-effects model, U_BM, was 0.12
• suggesting a high genomic mutation rate

• the rate of decline in mean viability was significantly lower than observed by Mukai
• the rate of increase in among-line variance was significantly higher
• U_BM estimate of 0.02 is much lower than the previous estimates
• the rate of mutations that detectably reduce viability may not be much greater than the lethal mutation rate (0.01 in these lines)
• the results also are consistent with models that include many mutations with very small effects

• the rate of lethal plus semilethal mutations per haploid second chromosome per generation can be estimated by using maximum likelihood analysis
• the resulting estimate of 0.010, with two log-likelihood support limits (analogous to 95% confidence limits) of 0.007-0.015, is significantly greater than the typically reported values of 0.004-0.006 for the second chromosome
• (Mukai 1964; Mukai et al. 1972; Crow & Simmons 1983; Ohnishi 1977)

• it is of some consequence whether one's underestimate of the genomic deleterious mutation rate is 0.1 (our estimate, scaled to the entire diploid genome) or almost one (the Mukai estimates, similarly scaled)