Study On MtDNA Genetic Diversity And Phylogeny Evolution Of Ten Domestic Sheep Breeds

In order to ascertain origin, sort and genetic relation of locality sheep breed in China, samples from 79 individuals of 8 different sheep breeds were collected from Gansu province(Lanzhou large tail sheep , LLT ), Ningxia province(Tan sheep , TS), Shanxxi province(Tong sheep , TTS),Shandong province(Small-tail han sheep , STH),Henan province(Large-tail han sheep,LTH), Xinjiang province(Aletail sheep,ALT; Small-tail han sheep,STH; Duolang sheep,DL),Qinghai province(Tibetan sheep,TBS) . And the Suffolk sheep and Dorset sheep from Yulin city in Shanxxi province as a control. Studying on the phylogeny evolution and population diversities among Chinese Domestic sheep breeds through analysising sequence of mtDNA D-loop HVI . the results showed that:1. All sequence data to GenBank,GenBank accession numbers:EF494774～EF494792,EF494802～EF494826,EF494875～EF600931,EF494842～EF600924,EF494866～EF600929,EF600912～EF600917。From the mean nucleotide compositions it could be concluded that there were enriched A and T in the mtDNA D-loop HVI .2. The length of the mtDNA D-loop sequences was considerable variable between 522bp and 683 bp, and nineteen molecule model. Except for minor insertions and deletions, the observed length variations were caused by different copy numbers of a 75 bp tandem repeat sequence. But it could not be considered as the characteristic sequence of haplotypes.3. The 93 individual sheep mtDNA D-loop HVI sequences found 63 haplotypes.and contained 73 variable sites, among them, singleton variable sites was 30, parsimony informative sites of two variants was 43. Except for insertions and deletions sites,the transition sites were 22 and transversion sites were 1, the ratio of transitions to transversions was 14.8,suggesting Chinese sheep has the high transition bias.4. The haplotype diversity and nucleotide diversity 93 individual sheep mtDNA D-loop HVI sequences were 0.981,0.02900.The average number of nucleotide differences variation was 9.309.The results indicate that the genetic diversity of Chinese sheep is very abundant.5. The NJ, UPGMA and ME phylogenetic trees was constructed by using MEGA 4.0 with goat as outgroup, three major lineages appeared in the 8domestic sheep, which termed A, B and C lineage. In order to improve the reliability of theresults, all the D-loop complete sequences were used to clustering which was O.musimon, O. vignei, O.aries from GenBank together with the sequences obtained in this study. The results showed that: the relationship between O.musimon and O.aries was nearer, because they were all in B lineage. All the analysis results indicated that the modern domestic sheep have the third maternal origin, and the genesis might be in China.