Study On The Chromosomes Of Eight Breeding Populations Of Sheep

The high-resolution peripheral blood lymphocyte culture method, chromosomal karyotypic with TdR (Thyinidine), MXT(Methotrexate) and 5′-BudR (5`-Bromo-2-Deoxyuridine). Banding techniques were used to study the chromosomal karyotypes, the cluster analysis of Karyotype Resemblance-Near coefficients, G-band ,C-band , and the polymorphism and cluster of Ag-NORs for GMM, SAMM, Suffolk, Dorset, Charolais, Corredale, SCC and Xiaoweihan yang. The high-resolution G-band ideogram was constructed. The result showed that the number of diploid chromosomes of seven breeds and one crossed sheep was 2n=54 (male 54, XY; female 54, XX). Among the total homologous pairs of autosome,1～3 chromosomes were metacentic chromosomes ; 4-26 homologous pair of autosome chromosomes were acrocentic chromosomes; X chromosome was the longest acrocentic chromosome, The Y chromosome was the smallest metacentic chromosme. The results of measuring chromosome and one-way ANOVA analysis showed that the relative length of all autosomes was different among the sheep breeds.The X chromosomes were similar and the Y chromosomes were different not only in relative length (p<0.01) but also in morphology. The result of the clustering analysis of eight breeds′karyotype resemblance-near cofficient and neighbor-joining method, NJ indicated that the eight breeds could be classified into four classes , according to the relationship and the terms of selection . Xiaoweihan yang was the oldest breed, the second was GMM; Dorset,SAMM, Charolais and SCC were the highly selected breeds; However, Suffolk and Corredale were in the middle station. The analysis of high-resolution G-banding illustrated that the appearance of banding patterns of all the chromosomes except for the Y chromosome were basically similar among the eight sheep breeds. Each pair of chromosomes could be identified by their characteristic bands. In this paper the G-bands ideogram of sheep were constructed. Total G-bands were 329(n). The analysis of C-banding showed that there was polymorphism among breeds. All of the autosomes gave positive C-bands. There was inserted C-bands on long arm of chromosome No.1 in Suffolk. The X chromosome showed negative C-bands . The Y chromosomes among eight breeds were positive except for GMM. Although the C-bands were located on the similar regions, they had polymorphism in shape and size.