deleterious mutation
Haag-Liautard C, Dorris M, Maside X, Macaskill S, Halligan DL, Houle D, Charlesworth B & Keightley PD 2007 Direct estimation of per nucleotide and genomic deleterious mutation rates in Drosophila. Nature 445:82-85.
- from 37 mutation events that we detected, we obtained a mean estimate for u of 8.4 × 10−9 per generation
- by multiplying u by an estimate of the fraction of mutations that are deleterious in natural populations of Drosophila10, we estimate that U is 1.2 per diploid genome
- assuming that point mutations and indels are equally deleterious on average, the mean genomic deleterious mutation rate is U = 1.15 (95% CI 0.49–2.19)
- indels are more likely to be strongly deleterious than point mutations
- including this information gives a slightly higher estimate for U of 1.20 (95% CI 0.51–2.28; Table 2)
- we found significant genetic variation in the mutation rate between genotypes
- our estimate of the nucleotide site mutation rate is about 5-fold (95% confidence limits 2-fold and 12-fold) higher than a phylogenetic estimate from synonymous site divergence
- assuming that wild flies undergo ten generations per year
- this could be partly due to inaccurate estimates of species divergence times
- or to differences in generation times between laboratory flies and wild flies
- our estimate for u indicates that U probably exceeds one event per diploid genome per generation in Drosophila and is unlikely to be less than 0.5
- this is comparable with an estimate in C. elegans based on direct sequencing
- genomic deleterious mutation rates estimated from the divergence of fitness traits in MA lines strongly disagree between these species
- about 0.01 in C. elegans
- up to about 1.0 in Drosophila
- it is unexpected that some Drosophila MA experiments should yield similar phenotypic6 and DNA-based (our study) estimates of U
- the reasons for this discrepancy remain obscure
- non-zero rates of recombination can be maintained by both Hill–Robertson interference11 and synergistic epistasis28
- with genomic deleterious mutation rates as low as 0.5
- (our lower confidence limit)
- our estimate of U = 1.2 seems too low for deterministic selection against deleterious mutations to allow the maintenance of sexual reproduction with a twofold cost
- although the mechanism might work if U were as high as our upper confidence limit