[Constrcution and application of Xinjiang fine-fleece sheep 2 times genome BAC library PCR screening system].

In this study, we used our special regional fostering breed Xinjiang fine-fleece sheep's genome to construct its genome library. The average size of insert fragments of the library was 133 kb. At the same time 92.5% clones' insert fragments of the library were larger than 100 kb and some larger than 300 kb. If we supposed sheep's genome contenting 3 x 10(6) kilo-base, on the basis of the average insert fragment was 133 kb the library covered 8 times genome of Xinjiang fine-fleece sheep. The probability of the tagged fragment being screened from the library was 98.208%. To prove the BAC library had been the better rate of coverage,four molecular markers: DMB_EX2, MCMA36, CP73 and BM1258 located to MHC gene of chromosome 20 near region in xinjiang fine-fleece sheep had been screened positive clones from the constructed 2 times genome library PCR screening system and the average positive clones was 1.5. The screening result showed that the constructed genome library was fairly closed to the 8 times genome coverage and had no erroneous tendency, which made the library being of the utmost useful resource for studying functional gene, position cloning and improving the genome physical map of sheep.