title: The rate and pattern of nucleotide substitution in Drosophila mitochondrial DNA.
abstract: The nucleotide sequences of a segment of mitochondrial DNA (mtDNA) have been determined for nine species or subspecies of the subgenus Drosophila of the genus Drosophila. This segment contains two complete protein-coding genes (i.e., NADH dehydrogenase subunit 1 and cytochrome b) and a transfer RNA gene (tRNA(ser)). The G+C content at third-codon positions for the two protein-coding genes was 1.5 times higher than that in the D. melanogaster species group, which belongs to the subgenus Sophophora. However, there was a substantial difference between the nucleotide frequencies of G and C. The number of nucleotide substitutions per silent site was more than three times higher than that for nuclear DNA, although it was only 60% of that for mammalian mtDNA. Both parametric and nonparametric analyses revealed a strong transition-transversion bias in nucleotide substitution, as was observed in mammalian mtDNA. Moreover, the rate of substitution of A and T for G and C is higher than that for the opposite direction. This bias seems to be responsible for the extremely A+T-rich base composition of Drosophila mtDNA. It is also noted that the rate of transitional change between A and G is higher than that between T and C.
authors.affiliation: Department of Biology, Tokyo Metropolitan University.
authors.forename: K
authors.initials: K
authors.lastname: Tamura
mesh_terms: D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D003062:Codon; D003573:Cytochrome b Group / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics*; D004330:Drosophila / Q000145:classification / Q000201:enzymology / Q000235:genetics*; D007700:Kinetics; D008969:Molecular Sequence Data; D009245:NADH Dehydrogenase / Q000235:genetics; D010802:Phylogeny; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D003062:Codon; D003573:Cytochrome b Group; D004272:DNA, Mitochondrial; D009245:NADH Dehydrogenase