Molecular genetic characterization of new bovine kappa-casein alleles CSN3F and CSN3G and genotyping by PCR-RFLP.

In order to characterize the two new kappa-casein variants F and G (CSN3F and CSN3G) recently detected in Ayrshire and Pinzgauer cattle, exon IV of CSN3 from heterozygous animals was amplified by polymerase chain reaction (PCR), cloned and sequenced. The sequencing data revealed single point mutations at nucleotide positions 10530 (G-->A) for CSN3F and 10790 (C-->T) for CSN3G, corresponding to amino acid exchanges in positions 10 (Arg-->His) and 97 (Arg-->Cys) respectively. These mutations alter recognition sites for the restriction enzymes HhaI and MaeII, which were subsequently used to confirm these polymorphisms in cattle carrying CSN3F or CSN3G. A PCR-restriction fragment length polymorphism (RFLP) genotyping procedure for all currently known CSN3 alleles (CSN3A, CSN3B, CSN3C, CSN3E, CSN3F, CSN3G) was developed.