Journal Article

Locus-Specific Decoupling of Base Composition Evolution at Synonymous Sites and Introns along the <i>Drosophila melanogaster</i> and <i>Drosophila sechellia</i> Lineages

Vanessa L. Bauer DuMont, Nadia D. Singh, Mark H. Wright and Charles F. Aquadro

in Genome Biology and Evolution

Published on behalf of Society for Molecular Biology and Evolution

Volume 1, issue , pages 67-74
Published in print January 2009 |
Published online May 2009 | e-ISSN: 1759-6653 | DOI: http://dx.doi.org/10.1093/gbe/evp008

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Selection is thought to be partially responsible for patterns of molecular evolution at synonymous sites within numerous Drosophila species. Recently, “per-site” and likelihood methods have been developed to detect loci for which positive selection is a major component of synonymous site evolution. An underlying assumption of these methods, however, is a homogeneous mutation process. To address this potential shortcoming, we perform a complementary analysis making gene-by-gene comparisons of paired synonymous site and intron substitution rates toward and away from the nucleotides G and C because preferred codons are G or C ending in Drosophila. This comparison may reduce both the false-positive rate (due to broadscale heterogeneity in mutation) and false-negative rate (due to lack of power comparing small numbers of sites) of the per-site and likelihood methods. We detect loci with patterns of evolution suggestive of synonymous site selection pressures predominately favoring unpreferred and preferred codons along the Drosophila melanogaster and Drosophila sechellia lineages, respectively. Intron selection pressures do not appear sufficient to explain all these results as the magnitude of the difference in synonymous and intron evolution is dependent on recombination environment and chromosomal location in a direction supporting the hypothesis of selectively driven synonymous fixations. This comparison identifies 101 loci with an apparent switch in codon preference between D. melanogaster and D. sechellia, a pattern previously only observed at the Notch locus.

Keywords: Drosophila; base composition; substitution rates

Journal Article.  6152 words.  Illustrated.

Subjects: Bioinformatics and Computational Biology ; Evolutionary Biology ; Genetics and Genomics

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