Study On Genetic Diversity And Molecular Phylogeny In Chinese Three Species Of Cattle

The mitochondrial DNA control region complete sequence of 84 individuals from 14 yellow cattle breeds or strains (including two foreign breeds) and 33 individuals from 5 Chinese yak breeds were individually determined. The results showed:The complete sequence of mtDNA D-loop of Chinese yellow cattle was 910 bp, 911bp and912 bp. 83 sites were polymorphic (9.10% in 910) with 19 singleton polymorphic sites and 64 parsimony informative polymorphic sites. There were five types of mutation of nucleotide. They were transition, transversion, insertion/deletion and the coexistence of transition and transversion. This research defined 45 haplotypes, in which haplotype H10 and H6 are major haplotypes of Chinese yellow cattle. Chinese native yellow cattle breeds include 38 haplotypes in which 32 haplotypes were the characteristic of their corresponding breeds. The distribution and frequency of all the haplotypes either within the breeds or between the breeds were unbalance. The average haplotypes diversity of the 14 yellow cattle breeds was 0.9593 ?.0126. The average genetic distance of haplotypes was 0.016(0.000-0.055). That indicated the abundance of D-loop haplotypes in Chinese yellow cattle. Average nucleotide differences and the nucleotide diversity in yellow cattle breeds were 19.675 and 2.164% respectively. Nucleotide divergence and Kimura 2-parameter distance between yellow cattle breeds were 0.292%~4.57% and 0.000~0.053 respectively. It indicated that genetic diversity of Chinese yellow cattle was very abundant. The curve of nucleotide mismatch distributions in yellow cattle population took on unimodal and wavilness. Tajima's test of selective neutrality was not significant (P>0.10). It revealed that yellow cattle population did not undergo expansions. The AMOVA results revealed that variance component among the breeds took 26.5% while within the breeds it took 73.5%. The results revealed that there were very significant differences(P>0.01). Further research on the Fst P value among the breeds revealed that there were not significant differences among most breeds while significant or very significant differences among a few breeds. It indicated that there was very significant divergence among Chinese yellow cattle breeds.This research had first time in the world determined yak's complete sequence ofmitochondrial DNA control region. It also adopted clone sequencing and reverse sequencing to testify the accuracy and credibility of the results. The length of yak's mitochondrial DNA complete sequence of control region was 891bp~895bp. Content of nucleotide T, C, A, G were 28.5%, 25.3%, 32.5% and 13.7% respectively. There were 47 polymorphic sites (5.23% in total analysed sites) with 11 singleton polymorphic sites and 36 parsimony informative polymorphic sites. They were transition, transversion and insertion/deletion. This research defined 24 haplotypes , in which haplotype H4 and H6 were major haplotypes of Chinese yak. The distribution of all the haplotypes among the breeds was disequilibration. The average diversity and genetic distance of haplotypes were 0.9687 ?0.0180 and 0.014(0.000-0.037) respectively, which indicated the abundance of haplotypes of yak's D-loop. The average nucleotide difference and the nucleotide diversity in Chinese yak breeds were 10.936 and 1.231% respectively. Nucleotide divergence and Kimura 2-parameter distance between yak breeds were 0.760-2.155%, and 0.003-0.029 respectively. It indicated that the genetic diversity of Chinese yak was very abundant.The nucleotide number of Chinese yak's control region complete sequence was 5-12bp less than that of Chinese yellow cattle. Yak's nucleotide variation rate (5.23%) was lower than yellow cattle's (9.10%). Yellow cattle's nucleotide diversity (2.164%) was higher than yak's (1.231%). It revealed that the genetic diversity was more abundant in Chinese yellow cattle than in Chinese yak.The partial sequence (420bp) of mitochondrial DNA cytochrome b (Cytb) had determined among 82 individuals from 13 yellow cattle breeds or strains (includi...