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Updated: Jul 18, 2026

The Green Monster Process for the Generation of Yeast Strains Carrying Multiple Gene Deletions
Published on: December 15, 2012
Transitions to asexuality result in excess amino acid substitutions
Susanne Paland1, Michael Lynch
1Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA. spaland@indiana.edu
Abstract:
Theory predicts that linkage between genetic loci reduces the efficiency of purifying selection. Because of the permanent linkage of all heritable genetic material, asexual lineages may be exceptionally prone to deleterious-mutation accumulation in both nuclear and organelle genes. Here, we show that the ratio of the rate of amino acid to silent substitution (Ka/Ks) in mitochondrial protein-coding genes is higher in obligately asexual lineages than in sexual lineages of the microcrustacean Daphnia pulex. Using a phylogeny-based approach to quantify the frequency of mutational-effect classes, we estimate that mitochondrial protein-coding genes in asexual lineages accumulate deleterious amino acid substitutions at four times the rate in sexual lineages. These results support the hypothesis that sexual reproduction plays a prominent role in reducing the mutational burden in populations.
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