Mitochondrial genes, mutations structure

In addition to the predictable variation in rate among the three codon positions there is also variation in the rate of evolution from codon to codon. Thomas and Beckenbach (1989) described spatial heterogeneity in the distributions of mutations from four mitochondrial protein genes in fishes. Spatial heterogeneity in the mitochondrial cytochrome b genes of a wide variety of vertebrates fits predictions based on previous structure/function models (Kocher et al. 1989, Irwin et al. in press). 

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