Sequence of Mammalian Mitochondrial DNA

The human mitochondrial (mt) genome consists of a closed circular duplex DNA approximately 10 x 106 daltons and has been the most intensely studied animal mt genetic system. The positions of the origin of replication of H strand synthesis (Crews et al. 1979), the 12S and 16S ribosomal RNA genes (Robberson et al. 1972) and 19 tRNA genes (Angerer et al. 1976) have been located on the genetic map shown in Figure 1. A number of discrete products of mitochondrial protein synthesis have been demonstrated and three of them identified as subunits 1, 2 and 3 of the cytochrome oxidase complex (Hare et al. 1980). In comparison with other mito-systems, genes for up to four subunits of the ATPase complex, one of the cytochrome bc1 complex and possibly for a ribosomal protein would be expected to be present (see review by Borst 1977). Both strands are thought to be completely transcribed symmetrically from a point near the origin of the H strand synthesis (Aloni and Attardi 1971; Murphy et al. 1975). These transcripts are then processed to give the rRNAs, the tRNAs and a number of polyadenylated but not capped mRNAs (Attardi et al. 1979). Both the L and H strands have been shown to be coding with the L strand containing the sense sequence of the rRNA genes, most of the tRNA genes and most of the stable polyadenylated mRNAs.