Fig. 5.—

Variation in RNA and protein-coding gene content in animal mitochondrial DNA. Left: taxonomic positions of groups with variable gene content. Central: variation in tRNA gene content. Middle: the presence of rRNA genes. Right: the presence/absence of protein-coding genes. Colored boxes highlight the identities of specific genes discussed in the text. Diagonally split boxes indicate genes that are absent in some lineages of the indicated group. Question marks denote genes for which presence or absence has not been confidently determined. Abbreviations: atp6, atp8–9: subunits 6, 8, and 9 of F0 adenosine triphosphatase (ATP) synthase; cob: apocytochrome b; cox1–3: cytochrome c oxidase subunits 1–3; nad1–6 and nad4L: NADH dehydrogenase subunits 1–6 and 4L; polB: DNA polymerase β; tatC: twin-arginine translocase component C; rns and rnl: SSU and LSU rRNAs. The tRNA genes are identified by the one-letter code for their corresponding amino acid; subscripts denote different genes for isoacceptor tRNAs, where I1 = trnI(CAU), I2 = trnI(GAU), L1 = trnL(UAG), L2 = trnL(UAA), R1 = trnR(UCG), R2 = trnR(UCU), S1 = trnS(UCN), S2 = trnS(UGA).