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Nat Genet. 2006 Jul;38(7):819-23. Epub 2006 Jun 11.

Parallel adaptive origins of digestive RNases in Asian and African leaf monkeys.

Author information

1
Department of Ecology and Evolutionary Biology, University of Michigan, 1075 Natural Science Building, 830 North University Avenue, Ann Arbor, Michigan 48109, USA. jianzhi@umich.edu

Abstract

Similar morphological or physiological changes occurring in multiple evolutionary lineages are not uncommon. Such parallel changes are believed to be adaptive, because a complex character is unlikely to originate more than once by chance. However, the occurrence of adaptive parallel amino acid substitutions is debated. Here I propose four requirements for establishing adaptive parallel evolution at the protein sequence level and use these criteria to demonstrate such a case. I report that the gene encoding pancreatic ribonuclease was duplicated independently in Asian and African leaf-eating monkeys. Statistical analyses of DNA sequences, functional assays of reconstructed ancestral proteins and site-directed mutagenesis show that the new genes acquired enhanced digestive efficiencies through parallel amino acid replacements driven by darwinian selection. They also lost a non-digestive function independently, under a relaxed selective constraint. These results demonstrate that despite the overall stochasticity, even molecular evolution has a certain degree of repeatability and predictability under the pressures of natural selection.

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PMID:
16767103
DOI:
10.1038/ng1812
[Indexed for MEDLINE]

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