Genotyping of bovine kappa-casein loci following DNA sequence amplification

Caseins are a family of milk proteins that exist in several molecular forms (alpha s1, alpha s2, beta and kappa) with variant alleles of each. Kappa-caseins (kappa-CN) exist as A or B variants and are of particular importance to the quality of the milk. We report a rapid non-radioactive method for differentiating bovine k-CN alleles. Unlike direct milk protein analysis, this method can be utilized for genotyping sperm, or animals of either sex at an early age. A 350bp fragment of the bovine kappa-CN gene was amplified by the polymerase chain reaction (PCR) technique. The amplified product digested with HinfI endonuclease generated restriction fragment length polymorphisms (RFLP's) that allowed precise identification of kappa-CN AA, AB or BB genotypes. Hybridization with allele specific oligo-probes confirmed the RFLP identification of genotypes. The accurate and early identification of milk protein genotypes can have a direct impact on dairy cattle breeding strategies.