PMID: 7932780Aug 1, 1994Paper

Analysis of directional mutation pressure and nucleotide content in mitochondrial cytochrome b genes

Journal of Molecular Evolution
L S JermiinR H Crozier


We present a new approach for analyzing directional mutation pressure and nucleotide content in protein-coding genes. Directional mutation pressure, the heterogenicity in the likelihood of different nucleotide substitutions, is used to explain the increasing or decreasing guanine-cytosine content (GC%) in DNA and is represented by microD, in agreement with Sueoka (1962, Proc Natl Acad Sci USA 48:582-592). The new method uses simulation to facilitate identification of significant A+T or G+C pressure as well as the comparison of directional mutation pressure among genes, even when they are translated by different genetic codes. We use the method to analyze the evolution of directional mutation pressure and nucleotide content of mitochondrial cytochrome b genes. Results from a survey of 110 taxa indicate that the cytochrome b genes of most taxa are subjected to significant directional mutation pressure and that the gene is subject to A+T pressure in most cases. Only in the anseriform bird Cairina moschata is the cytochrome b gene subject to significant G+C pressure. The GC% at nonsynonymous codon sites decreases proportionately with increasing A+T pressure, and with a slope less than one, indicating a presence of selective constra...Continue Reading

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