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Small fitness effects and weak genetic interactions between deleterious mutations in heterozygous loci of the yeast Saccharomyces cerevisiae

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posted on 2010-11-15, 11:37 authored by Krzysztof Szafraniec, Dominika M. Wloch, Piotr Sliwa, Rhona H. Borts, Ryszard Korona
Rare, random mutations were induced in budding yeast by ethyl methanesulfonate (EMS). Clones known to bear a single non-neutral mutation were used to obtain mutant heterozygotes and mutant homozygotes that were later compared with wild-type homozygotes. The average homozygous effect of mutation was an approximately 2% decrease in the growth rate. In heterozygotes, the harmful effect of these relatively mild mutations was reduced approximately fivefold. In a test of epistasis, two heterozygous mutant loci were paired at random. Fitness of the double mutants was best explained by multiplicative action of effects at single loci, with little evidence for epistasis and essentially excluding synergism. In other experiments, the same mutations in haploid and heterozygous diploid clones were compared. Regardless of the haploid phenotypes, mildly deleterious or lethal, fitness of the heterozygotes was decreased by less than half a per cent on average. In general, the results presented here suggest that most mutations tend to exhibit small and weakly interacting effects in heterozygous loci regardless of how harmful they are in haploids or homozygotes.

History

Citation

Genetical Research (2003), 82(1), pp. 19-31.

Published in

Genetical Research (2003)

Publisher

Cambridge University Press

issn

0016-6723 (print);1469-5073 (electronic)

Copyright date

2003

Available date

2010-11-15

Publisher version

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=175907&fileId=S001667230300630X

Language

en

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