deleterious mutation

García-Dorado A & Caballero A 2000 On the average coefficient of dominance of deleterious spontaneous mutations. Genetics 155:1991-2001.

• the results of these experiments, although inconsistent, have been interpreted as indicating slight recessivity of deleterious mutations, with h ≈ 0.4
• we have reanalyzed Ohnishi's data, estimating h by the regression method, and obtained a much smaller estimate of ~0.1
• this significant difference can be due partly to the different weighting implicit in the estimates
• we suggest that this is not the only explanation
• a putative nonmutational decline in viability occurring in the first half of Ohnishi's experiment (affecting both homozygotes and heterozygotes) has biased upward the estimates from the ratio, while it would not bias the regression estimates
• this hypothesis also explains the very high h ≈ 0.7 observed in Ohnishi's high-viability chromosomes
• a model of few mutations with moderately large effects and h ≈ 0.2 is able to explain the observed estimates and the distributions of homozygous and heterozygous viabilities