[Different evolution rule of SRY gene between hominoid and Old World monkey]

The complete SRY gene of P. nemaeus and M. arctiodes were amplified by using PCR and sequenced. Combined with the same regions of other primate animals, sequence analysis confirmed the conservation of HMGbox. In molecular phylogenetic tree constructed, we made the Ka/Ks value pairwise comparison of HMGbox flanking sequences both intra- and inter- Hominoid and the Old World monkey. To our interest, the pairwise comparison of species in Hominoid suggested a higher Ka/Ks ratio than that in the Old World monkey or between the Old World monkey and marmoset, which showed existent of different pattern of evolution. In addition, in Hominoid Ka/Ks ratio for HMGbox sequences was obviously on the increase. The rate of nonsynonymous substitutions per nonsynonymous site is faster than that of synonymous substitutions per synonymous site in Hominoid (driven by positive directional selection). Our analysis suggested that it might be resulted from functional change of this gene and the system error or the close relationship among Hominoid species. It is also supposed that the positive selection was functioned at the beginning of the divergence of Hominoid species.