Abstract:

【Objective】 There is a foot-rot disease in the population of Tibetan sheep, which leads to the loss of sheep on death. Gene OLA-DQA2 is associated with foot-rot disease. The polymorphism and variation of gene OLA-DQA2 exon 2 was investigated in order to find the best alleles for foot-rot resistance in the further observation by means of phenotype and genotype. 【Method】 Fragments of DNA containing OLA-DQA2 exon 2 were amplified using PCR. Single-strand conformational polymorphism (SSCP) analysis and DNA sequence analysis were employed to detect genetic variation in 216 Tibetan Sheep (including ones with foot-rot). 【Result】 Fifteen nucleic acid sequences were identified. Eight novel alleles were found for the first time, respectively named OLA-DQA2*H, *I, *J, *K, *L, *M and *N. Thus the number of alleles identified is increased from 23 to 31. Seventeen-one nucleotide polymorphisms were found in the analysis of gene sequences, which mainly came from point mutation, including transition of 39 (54.9%) and 23 of transversion (32.4 %). 【Conclusion】 Tibetan sheep DQA2 gene exon 2 has high level of sequence polymorphism. The population may have strong resistance to genetic resources. The best alleles will be found by further observation from phenotype and genotype of the DQA2 gene in the near future. Consequently, the plan of disease resistance will be carried out in sheep breeding practice.

Key words: DQA2 gene, genetic polymorphism, PCR-SSCP, foot rot, tibetan sheep