The Levels Of Genetic Differentiation Of Small Tailed Han Sheep And Tan Sheep Populations

Using the method of " random sampling in typical colonies of the central area of the habitat " and several electrophoresis techniques, the variations of 17 structural loci encoding blood proteins in 60 Small Tailed Han sheep and 73 Tan sheep were examined and compared with those of 14 other sheep populations in China and other countries to explore their relations of genetic differentiation. The average heterozygosities (h) of Small Tailed Han sheep and Tan sheep were 0.2360 and 0.2587, respectively. Their average polymorphic information contents (PIC) were separately 0.1974 and 0.2102. Their average effective number of alleles (Ne) valued 1.5723 and 1.5751 each. The coefficients of gene differentiation of four groups (including 4, 6, 13, 16 sheep populations, respectively) were 0.049323, 0.059987, 0.1728 and 0.201256, respectively, which indicated that the level of gene differentiation at the structural loci among Hu sheep, Tong sheep, Small Tailed Han sheep and Tan sheep was low, the level of gene differentiation among above-mentioned four sheep populations and Mongolian sheep higher, and the level of gene differentiation among sheep belonging to Mongolian sheep group, South Asian sheep and European sheep highest. Earlier researchers proposed that Small Tailed Han sheep and Tan sheep both evolved from Mongolian sheep, the proposition was further verified by the results in this study. Hu sheep, Tong sheep, Small Tailed Han sheep and Tan sheep were decreasingly affected by the bloodline of Mongolian sheep. The relationships between sheep populations were not closely related to the distances between sheep populations.Using seven microsatellite markers, we examined the genetic variations of Small Tailed Han sheep and Tan sheep and estimated their gene frequencies. The same data of Hu sheep, Tong sheep and Yangtse River Delta White goat, which served as the referenced population, were cited to further explore their levels of genetic differentiation. The mean heterozygosities of Small Tailed Han sheep and Tan sheep were 0.9336 and 0.9116, respectively. The polymorphic information content values were parallel to the heterozygosities. The mean effective number of alleles valued 16.4532 and 11.6884, respectively. The values of these three parameters showed the degree of genetic variation in Small Tailed Han sheep in non-coding regions was higher than that in Tan sheep. The coefficient of gene differentiation among four sheep populations was 0.026329, and that among sheep and goat populations was 0.039036, indicating that the degree of gene differentiation was comparatively low among sheep populations and that among sheep and goat populations higher. The relationships of the pair Hu-Tong sheep and Small Tailed Han-Tan sheep were both close. The latter, however, needed further verification. Further, we calculated the relative evolution distance (RED) of the above sheep populations. RED is defined as a ratio of the converse of the confidence level value( n) of the fuzzy cluster among the infraspecific populations to the converse of the least confidence level value( ) among a referenced population of closely related species and all the infraspecific populations. RED between Hu sheep and Tong sheep was 0.253, that between Small Tailed Han sheep and Tan sheep 0.407, and that between Hu sheep-Tong sheep and Small Tailed Han sheep-Tan sheep 0.462.The gene frequencies of 13 structural loci and 7 microsatellite loci in Small Tailed Han sheep, Tan sheep, Hu sheep and Tong sheep, which were sampled by the method " random sampling in typical colonies of the central area of the habitat ", were comparatively analyzed and discussed to verify the relationships of genetic differentiation among populations. The results showed the heterozygosity, polymorphicinformation content, effective number of alleles at each microsatellite locus and their average were higher than those at each structural locus, which indicated that the levels of population variations revealed by the microsatellite loci were higher than those by the structural l...