, Volume 2, Issue 1, pp 37-55

Cytochromeb gene of marine mammals: Phylogeny and evolution

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The DNA sequences of the mitochondrial cytochromeb gene of marine mammals (Cetacea, Pinnipedia, Sirenia) were compared with cytochromeb genes of terrestrial mammals including the semiaquatic hippopotamus. The comparison included 28 sequences, representing 22 families and 10 orders. The dugong (order Sirenia) sequence associated with that of the elephant, supporting the Tethytheria clade. The fin whale and dolphin (order Cetacea) sequences are more closely related to those of the artiodactyls, and the comparison suggests that the hippopotamus may be the extant artiodactyl species that is most closely related to the cetaceans. The seal sequence may be more closely related to those of artiodactyls, cetaceans, and perissodactyls than to tethytheres, rodents, lagomorphs, or primates. The cytochromeb proteins of mammals do not evolve at a uniform rate. Human and elephant cytochromeb amino acid sequences were found to evolve the most rapidly, while those of myomorph rodents evolved slowest. The cytochromeb of marine mammals evolves at an intermediate rate. The pattern of amino acid substitutions in marine mammals is similar to that of terrestrial mammals.