Short communication: characterization of a kappa-casein genetic variant in the Chinese yak, Bos grunniens

A PCR-single strand conformation polymorphism protocol has been developed for rapid genotyping of the yak kappa-casein gene. A total of 307 yaks from the Tianzhu White, Jiulong, Maiwa, and Datong breeds in China were genotyped at the kappa-casein locus using the protocol developed in the present study. A polymorphism of kappa-casein gene exon 4 has been identified in Tianzhu White breed by evaluating genomic DNA. The polymorphic site consists of a single nucleotide substitution G--C at position 362 of the exon 4, resulting in an AA substitution from Arg to Pro at position 121 of the AA sequence and in 2 alleles named, respectively, G and C based on nucleotide 362. The occurrence of allele C in the Tianzhu White breed was high with an allele frequency of 0.15. However, allele C appears to be absent in the yaks from Jiulong, Maiwa, and Datong breeds.