Structure and evolution of the avian mitochondrial control region

The structural and evolutionary characteristics of the mitochondrial control region were studied by using control region sequences of 68 avian species. The distribution of the variable nucleotide positions within the control region was found to be genus specific and not dependant on the level of divergence, as suggested before. Saturation was shown to occur at the level of divergence of 10% in pairwise comparisons of the control region sequences, as has also been reported for the third codon positions in ND2 and cytochrome b genes of mtDNA. The ratio of control region vs cytochrome b divergence in pairwise comparisons of the sequences was shown to vary from 0.13 to 21.65, indicating that the control region is not always the most variable region of the mtDNA, but also that there are differences in the rate of divergence among the lineages. Only two of the conserved sequence blocks localized earlier for other species, D box and CSB-1, were found to show a considerable amount of sequence conservation across the avian and mammalian sequences. Additionally, a novel avian-specific sequence block was found.