Mitochondrial-Dna Sequence Comparison Among the Great Apes and Man.

Mitochondrial DNA (mtDNA) sequence comparisons reveal patterns of sequence divergence during the evolution of the small subunit ribosomal RNA gene (12S rDNA), the non-coding region, and the phenylalanyl tRNA (tRNAphe) along the gorilla, pygmy chimpanzee, common chimpanzee and human lineages. The relative rates and modes of sequence divergence vary among these mtDNA regions, although transition-type substitutions are the most prevalent type of event observed in sequence divergence of all regions examined. The non-coding region of mtDNA has evolved more rapidly than the tRNA and 12S rRNA genes by nucleotide substitution and has been the site of extensive insertion/deletion events. The mitochondrial tRNAphe and 12S rRNA mtDNA genes are conserved, relative to the non-coding region, but the level of accumulation of substitutions and small insertions/deletions is much higher than that of the nuclear 18S rRNA and tRNA genes. A non-r and om distribution of sequence substitution and deletions/insertions in the non-coding region has resulted in blocks of highly conserved sequences amidst hghly divergent regions. These conserved sequences may be important for initiation of mtDNA replication and transcription. The distribution of sequence variation in the mitochondrial 12S rRNA and tRNAphe genes may reflect evolutionary conservation of functionally important RNA secondary structures. Pairwise comparisons of the number of substitutions in the mt 12S rRNA gene of the great apes and man show the gorilla, human, and chimp lineages are approximately equally related. Phylogenetic reconstruction of the ancestral relationships of these hominoid species indicates an almost (a trichotomous) equivalent time of divergence of the human, gorilla, and chimp lineages.Ph.D.GeneticsUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/159567/1/8324202.pd