Sequence analysis of 12 structural genes and a novel non-coding region from mitochondrial DNA of Atlantic cod, Gadus morhua.

We have determined the nucleotide sequences of 12 structural genes from the mitochondrial DNA of Atlantic cod, Gadus morhua. These genes encode the proteins NADH dehydrogenase subunit 2, cytochrome c oxidase subunit I, cytochrome c oxidase subunit II, and apocytochrome b, as well as the transfer RNAs tRNA(Ile), tRNA(Gln), tRNA(Met), tRNA(Ser) (UCN), tRNA(Asp), tRNA(Glu), tRNA(Thr) and tRNA(Pro). The apocytochrome b sequences were used to construct a phylogenetic tree revealing the evolutionary divergence between modern bony fishes, sturgeon and sharks. We found that bony fishes display the same slow amino acid substitution rates in the mitochondrial encoded proteins as cartilaginous fishes (sharks). A novel non-coding region of 74 base pairs not found in other fishes where sequence data are available is located between the genes encoding tRNA(Thr) and tRNA(Pro). This region contains both direct and inverted repeat motifs that may function in termination of the H-strand transcript.