Isolation and characterization of polymorphic microsatellites in the genome of yak (Bos grunniens).

The researches on yak genetics and breeding were extremely restricted due to lacking of reliable DNA molecular markers. The microsatellites with repeat motif (AC)n/(GT)n in yak genome were enriched by Dynal magnetic beads and the gene libraries containing (AC)n/(GT)n were constructed. Among the 92 identified and sequenced positive clones, 40 contained perfect repeats (43.48%), 41 contained imperfect repeats (44.57%) and 11 contained compound repeats (11.96%). As compared with the percentage of perfect repeats, no significant increases of imperfect repeats were observed in yak genome, which indicated that the level of adaptive evolution of the ability to repair damaged genomic DNA for yaks were high enough to endure the natural pressure of nucleotide substitution resulted from ultraviolet irradiation in high-altitude areas. Totally 19 polymorphic microsatellite loci were screened and genotyped on the basis of electropherograms on an ABI 310 Genetic Analyzer. All the loci exhibited moderate to high-level polymorphisms in a test population of Bos grunniens and the polymorphic information content ranged from 0.299 to 0.861 (mean 0.678). The newly isolated (AC)n/(GT)n repeats from yak genome will display their potential values in examining intra-population genetic structure and inter-population relationships, and also in investigating molecular markers for production and adaptive traits of individual/population.