Origin And Phylogeny Analysis Of Yak

Yak is the only one of bovinae that can multiply on the high and cold pasturing area of Qingzang altiplano, and have "altiplano boat" and "almighty domestic animal" beauty. Yak is origined from china, it is an old and original cattle. It is hard to make sure the origin and relationship between yak and other species in the bovinae, and there is also much dispute on it. It is also become a study hotspot of the bovinae molecule evolvement and phylogeny. There are two different point: one is that Yak has the nearer relationship to Bos; the other is that yak has the nearer relationship to Bison.Animal mtDNA have some characteristics, such as the rapid evolvement rate, great variation in the colony, simple molecule structure, so it has become an important molecule marker in researching species origin, molecule evolvement and phylogeny analysis. The D-loop control regain is abundant of "A" and "T", its mutation rate is 5-10 times of other coding regains in mtDNA, so it has been applied to the phylogeny research of category, and interspecies. We performed PCR amplification and sequence to the yak's D-loop in mtDNA, then performed sequence variation and phylogeny analysis to the D-loop, the first and second varied sequences of bovinae. As a result, the length of bovinae D-loop sequences varied from 890bp to 1015bp, 226 polymorphic sites were discovered, the percentage of polymorphic sites is 22.47%, show that the polymorphism is very abundant in bovinae mtDNA D-loop regain, based on the sequence alignment and genetic distance results, we find that the yak(Bos mutus and Bos grunniens) has a nearer relationship to Bison bison, and farther to Bos. Based on the bovinae D-loop molecule evolvement bell of 10.6% per mega year, we speculate that the divergence time between Bos mutus and Bos grunniens is about 0.35 mega year ago. We built the phylogeny tree based on the bovinae mtDNA D-loop sequence and the first and second varied sequence, it show that Bos mutus and Bos grunniens cluster first, then they cluster with Bison bison, and then cluster with embranchment which contains Bos taurus and Bos indicus, it's also explain that the yak has higher genetic comparability to Bison bison than Bos, and has nearer relationship to Bison bison than Bos. Depend on the molecule evolvement bell, We speculate that Bos grunniens diverge to Bos taurus is about in 0.53 MYA, diverge to Bos indicus is about 0.47MYA, diverge to Bison bison is about 0.32MYA, diverge to Bubalus bubalis is about in 0.86MYA, the divergence time between Bos taurus and Bos indicus is about in 0.24MYA.Y chromosome followes male-inherit, and most of it is non-recombining region, not able to be influenced by recombine and reversion-mutation, the mutation rate is low, also can inherited more stable than marker in the euchromosome, is loyalty registrar of evovement events. We performed PCR amplification and sequence to TSPY and DBY partial sequence in the yak Y chromosome, and performed sequence variation and phylogeny analysis to the bovinae. We find that Bos grunniens and Bison bison have the nearest common ancestor. Based on the bovinae TSPY molecule evolvement bell, we confer that the divergence time between Bos grunniens and Bison bison is about in 1.16MYA. Depend on the sequence variation and genetic distance results, we speculate that the genetic comparability and relationship of Bos grunniens is nearer to Bison than to Bos. We built phylogeny tree of bovinae based on TSPY and DBY sequences, the tree shows that the yak has nearer relationship to Bison than to Bos. Depend on the TSPYmolecule evolvement bell, We speculate that Bos grunniens diverge to Bos taurus is about in 2.09 MYA, diverge to Bos indicus is about 1.86MYA, diverge to Bubalus bubalis is about in 16.44MYA, the divergence time between Bos taurus and Bos indicus is about in 1.16MYA.MHC, a region with the most abundant polymorphism and important function in the genome, mainly involve in immune response of organism, and has been used in the research of disease resistance, genetic structure investigation, defining the consanguinity, and evolution process of species. In this research, we first sequenced DRB Upstream Regulatory Region (URR) of 11 Yaks, and conduct a Phylogenetic analysis among different species. The result suggested that we found 3 haplotypes in the 11 sequenced BoLA-DRB-URR; There exist highly conserved sequence motifs including W, X, Y, CCAAT and TATA-like boxes in the obtained sequences obeying rigid organization. The phylogeny Analysis show that the sequences of bovinae first cluster with the sequences of ovis, and then cluster with swine, It's accord to zoology taxonomy result, proved that the sequences we got are BoLA-DRB-URR.