This study is based on the Tong sheep obtained by the random sampling method of typical colonies in the central area of Baishui County in Shaanxi Province, China. An investigation was undertaken to clarify the gene constitution of blood protein and nonprotein types of Tong sheep. Twelve genetic markers were examined by starch-gel electrophoresis and cellulose acetate electrophoresis. Polymorphism in Tong sheep was found at the following 10 loci, transferrin （Tf）, alkaline phosphatase （Alp）, leucine aminopeptidase （Lap）, arylesterase （Ary-Es）, hemoglobin-β （Hb-β）, X-protein （X-p）, carbonic anhydrase （CA）, catalase （Cat）, malate dehydrogenase （MDH）, and lysine （Ly）, whereas, albumin （A1） and postalbumin （Po） loci were monomorphic. Genetic approach degree method and phylogenetic relationship clustering method were used to judge the origin and phylogenetic status of Tong sheep. Results from both methods maintained that Tong sheep belonged to the ＂Mongolia group＂, and Mongolia sheep was the origin of Tong sheep. This was also supported by the history of Tong sheep breeding. Compared to the phylogenetic relationship clustering method, the genetic approach degree method was more reliable for the extraction from East and South of Central Asia, and was more effective in reflecting the breeding course of Tong sheep.
This paper was based on the Hu sheep in China, after collecting the same data about 9 Asia sheep populations and 5 European sheep (breeds in Japan) populations. It clustered 15 populations in terms of the gene frequency of 10 loci and 33 allele in blood enzyme and other protein variations. The result of Hierarchy Clustering showed that the sheep populations in the East and South of Central Asia could be classified into three genetic groups: Mongolia sheep, South Asia sheep and European sheep, and the Hu sheep belonged to Mongolia sheep.
Gene frequencies of Hu sheep and Tong sheep were obtained with“Random sampling in typical colonies of a central area”. Of the 12 loci tested in Hu sheep, 11 loci were polymorphic. Reliability of the estimated frequencies of 27 alleles reached 0.95 except for PoF, TfA,Tff,Hb-βA and CAF which had reliabilities of 0.5222,0.7478,0.5222,0.6212 and 0.899, respectively. Of the 12 loci tested in Tong sheep, 11 loci were polymorphic. Reliability of the estimated frequency of 25 alleles reached 0.95 except for TfA, TfE and CAF which had reliabilities of 0.931,0.6922 and 0.7924, respectively. The average heterozygosity () and average homozygosity (J) was computed and the J of the two sheep colonies was 0.6619 and 0.6448, respectively. Consistent with our conclusions based on genetic data, previous research divided the native sheep populations of East and South Central Asia into three group: the“Mongolian group”,“South-Asian group” and“European group”. Consequently, the degree of genetic similarity between populations and known groups would seem to provide a reliable means of determining the genetic relationships between populations and may reflect the true genetic origin of Hu sheep and Tong sheep in China [Acta Zoologica Sinica 49(1):134-138,2003].
In the present study with Tan sheep, small-tailed Han sheep, Hu sheep, Tong sheep, and Wadi sheep, we detected the distribution of gene frequency of several microsatellite sites in different chromosomes, the result showed that： 1） Hu sheep was in the status of Hardy-Weinberg extreme disequilibrium （P 〈 0.01）, while populations including Tong sheep, small-tailed Han sheep, Tan sheep, and Wadi sheep were in Hardy-Weinberg equilibrium （P 〉 0.05）. 2） Variance analysis of the heterozygosity and poly- morphic information content at rnicrosatellite makers showed that there were not significant differences among populations as to heterozygosity and PIC （P 〉 0.05）, as to effective number of alleles there were not significant differences both among Tan sheep, Hu sheep, Tong sheep, and Wadi sheep, and between Wadi sheep and small-tailed sheep （P 〉 0.05）, but between the former three populations and the latter two populations, there were significant differences （0.01〈 P 〈0.05）. The variation levels of small-tailed Han sheep was the highest in the five populations based on microsatellite maker data, subsequently followed by Wadi sheep, Tong sheep, Tan sheep, and then Hu sheep. 3） The phylogenetic relationships of the five sheep populations in this study did not meet the mechanism of isolation by distance, and the genetic differentiation relationships among five sheep populations were not closely linearly correlative with their geography distribution. Our findings supported related records in literature： The five populations originated on different time stage from the primogenitor population and communicated genetically with each other thereafter in the process of natural and artificial selection and on different ecological environment.
