deleterious mutation

Fry JD & Nuzhdin SV 2003 Dominance of mutations affecting viability in Drosophila melanogaster. Genetics 163:1357-1364.

• we investigated whether transposable element (TE) insertions have higher average dominance for egg-to-adult viability than do point mutations
• a possibility suggested by the types of fitness-depressing effects that TEs are believed to have
• a traditional regression method gave a dominance estimate for all mutations of 0.17, whereas average dominance of copia insertions was 0.51
• because a considerable fraction of spontaneous mutations are caused by TE insertions, whereas EMS induces mainly point mutations, we predicted that average dominance would decline with increasing EMS concentration
• this pattern was observed, but again fell short of formal significance (P = 0.07)

• TEs would have been highly expressed in the repulsion crosses, giving rise to negative, nearly additive fitness effects, but much less expressed in the coupling crosses
• although we will never know the explanation with certainty, this hypothesis seems more plausible to us than Mukai and Yamazaki's (1968) hypothesis that the effects of nonallelic mildly deleterious mutations differ depending on whether they are located in cis or in trans