Abstract: SRY (sex-determining region on the Y chromosome) gene is located on Y chromosome of mammal and plays very important role of sex determination. With cloned and sequenced SRY gene, then analyzed the sequence by bioinformatics, meanwhile, knew the codon usage bias of SRY gene coding region in Maiwa yak, cattle, sheep, goats, pigs, mice, chicken and human. The results of the Maiwa yak SRY gene, contained an open reading frame(ORF) of 690 bp which it encoded 229 amino acids. The SRY nucleotide sequence of coding region was compared among Maiwa yak, cattle, sheep, goat, pig, mice, chicken and human. The identity of nucleotide sequences of the coding region of SRY gene between Maiwa yak and cattle, sheep, goat, pig, mice, chicken and human were 99.9%, 93.9%, 91.2%, 76.5%, 43.3%, 21.4%, 69.1%, respectively. Phylogenetic tree analysis showed that firstly Maiwa yak and cattle were belonged to a branch, sheep and goats were clustered into one group, and then these two categories were got together with pig, human and mice were belonged to a branch, finally clustered into a group with chicken, the results was consistent with the results of the conventional biological classification. After protein analysis resulted that gene encoded protein formula for molecular was C₁₁₅₅H₁₈₂₇N₃₅₁O₃₄₈S₁₁, molecular mass was 2655.0, theoretical PI was 9.55. the hydrophilic average -0.855. Codon preference analysis, the T3_s was 0.2905, the C3_s was 0.3240, the A3_s was 0.3728, G3_s was 0.2963, GC content of 48%, the number of synonymous codon was 61. Meanwhile,the reason that the SRY nucleotide sequences of the coding region was conservative and there was higher identity in Maiwa yak and cattle, sheep, goat, pig, human. The third nucleotide of the codon frequency of occurrence of A was greater than G. The SRY gene encoded a hydrophilic protein.

Key words: Maiwa yak; SRY gene; cluster analysis; codon usage bias