The complete mitochondrial DNA sequence of Atlantic cod (Gadus morhua): relevance to taxonomic studies among codfishes.

We have determined the complete sequence of an Atlantic cod (Gadus morhua) mitochondrial genome. The 16,696-bp genome contains the same 37 mitochondrial structural genes found in all other vertebrates analyzed, in an organization similar to that of the placental mammals. The cod mitochondrial DNA (mtDNA) contains variable numbers of a 40-bp heteroplasmic tandem repeat motif located in the major noncoding region, and the sequence presented here includes four repeats. Comparison among the major noncoding region in mtDNAs from different codfishes, as well as different stock samples of Atlantic cod, reveals conserved sequence features. The central region of the noncoding region as well as a spacer region located between the tRNAThr and tRNAPro genes appear to be variable in sequence, and are good candidates for high-resolution markers in population studies. Atlantic cod is the first marine bony fish whose mitochondrial genome is completely sequenced.