Sequence and arrangement of the genes for cytochrome b, URF1, URF4L, URF4, URF5, URF6 and five tRNAs in Drosophila mitochondrial DNA.

The nucleotide sequence of a segment of the mtDNA molecule of Drosophila yakuba has been determined, within which have been identified the 3' end of the large rRNA gene and the entire genes for tRNAleuCUN , URF1 , tRNAserUCN , cytochrome b, URF6 , tRNApro, tRNAthr , URF4L , URF4 , tRNAhis and URF5 . The genes are arranged in the order given, with the large rRNA gene being closest to the A+T-rich region which contains the origin of replication. Transcription of all of these genes except those for cytochrome b, URF6 , tRNAserUCN and tRNAthr proceeds in the same direction as replication. Differences occur in the relative arrangement and in the direction of transcription of these twelve genes between D. yakuba and mammalian mtDNA molecules. Internal AGA codons occur in all of the polypeptide genes except URF6 . Comparisons of the positions of these AGA codons to codons in corresponding mouse genes is consistent with the view that in the D. yakuba mitochondrial genetic code AGA specifies serine. Genes equivalent to all of the polypeptide, tRNA and rRNA genes found in mammalian mtDNA have now been identified in D. yakuba mtDNA.