Single nucleotide polymorphisms in the ovine casein genes detected by polymerase chain reaction-single strand conformation polymorphism

Casein genetic polymorphisms are important and well known due to their effects on quantitative traits and technological properties of milk. At the DNA level, polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) allows for the simultaneous typing of several alleles at casein loci, as well as the detection of unknown polymorphisms. Here we describe the usefulness of the PCR-SSCP technique for casein typing in sheep. In particular, three single-nucleotide polymorphisms (SNP) are described at CSN1S1, CSN2, and CSN3, all resulting in amino acid exchanges. At CSN1S1, a transition T -> C was found, resulting in the deduced amino acid exchange Ile186 -> Thr186. A transition A -> G resulting in the deduced amino acid exchange Met183 -> Val183 was identified at CSN2. The 2 SNP showed a rather high frequency (ranging from 0.12 to 0.26) in 3 Italian breeds (Sarda, Comisana, Sopravissana). Another transition C -> T (Ser 104 -> Leu104) was found at CSN3 in one heterozygous animal.