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Adaptive protein evolution at the Adh locus in Drosophila.

Authors
  • McDonald, J H
  • Kreitman, M
Type
Published Article
Journal
Nature
Publication Date
Jun 20, 1991
Volume
351
Issue
6328
Pages
652–654
Identifiers
PMID: 1904993
Source
Medline
License
Unknown

Abstract

Proteins often differ in amino-acid sequence across species. This difference has evolved by the accumulation of neutral mutations by random drift, the fixation of adaptive mutations by selection, or a mixture of the two. Here we propose a simple statistical test of the neutral protein evolution hypothesis based on a comparison of the number of amino-acid replacement substitutions to synonymous substitutions in the coding region of a locus. If the observed substitutions are neutral, the ratio of replacement to synonymous fixed differences between species should be the same as the ratio of replacement to synonymous polymorphisms within species. DNA sequence data on the Adh locus (encoding alcohol dehydrogenase, EC 1.1.1.1) in three species in the Drosophila melanogaster species subgroup do not fit this expectation; instead, there are more fixed replacement differences between species than expected. We suggest that these excess replacement substitutions result from adaptive fixation of selectively advantageous mutations.

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