TITLE:
Natural selection in vertebrate evolution under genomic and biosphere biases based on amino acid content: Primitive vertebrate hagfish (Eptatretus burgeri)
AUTHORS:
Kenji Sorimachi, Teiji Okayasu, Shuji Ohhira, Nobuhide Masawa, Ichio Fukasawa
KEYWORDS:
Natural Selection; Vertebrate Evolution; Complete Mitochondrial Genome; Amino Acid Composition; 16S rRNA; Hagfish (Eptatretus burgeri)
JOURNAL NAME:
Natural Science,
Vol.5 No.2,
February
26,
2013
ABSTRACT: Cluster analyses using the amino acid content predicted from the coding
regions (13 genes) of complete vertebrate mitochondrial genomes as traits
grouped selected vertebrates into two clusters, terrestrial and aquatic
vertebrates. Exceptions were the hagfish (Eptatretus
burgeri), thought to be an early ancestor of vertebrates, and the black
spotted frog (Rana nigromaculata),
which is terrestrial as an adult and aquatic as a larva. These two species fall
into the terrestrial and aquatic clusters, respectively. Using the nucleotide
(G, C, T and A) content in the coding and non-coding regions, and in the
complete genome as traits, similar results were obtained but with some additional exceptions. In addition, phylogenetic
analyses of 16S rRNA sequences produced a consistent result. The results of
this study indicated that vertebrate evolution is controlled by natural
selection under both an internal bias as a result of nucleotide replacement
genomic rules, and an external bias caused by environmental biospheric conditions.