Identification of the goat CSN1S1F allele by means of PCR-RFLP method.

The relative amounts of the four casein fractions (as1, b, as2 and k) affect the physico-chemical, nutritional and technological properties of milk of domestic ruminants. Polymorphism at the CSN1S1 locus in goat species is of interest because of its high degree of polymorphism and differences in the level of protein synthesis. The A, B and C alleles are associated with a ‘high’ level of as1-casein in milk (around 3.5 g:l), the E allele with a ‘medium’ level (1.1 g:l), the F and G alleles with a ‘low’ level (0.45 g:l), 01 and 02 alleles being ‘null’ alleles, without as1-casein in the milk of homozygotes. Recently, the B allele has been divided into four alleles: B1 (considered as the ancestor allelic form), B2 (previously idenfied as B), B3 and B4. A single nucleotide deletion (C) at the 23rd nucleotide of the ninth exon and two insertions, one of 11 bp (CGTAATGTTTC), located 73 nucleotides downstream of the 5% splice site of the ninth intron, and the other of 3 bp (AAT or TAA), interrupting the long polypyrimidine stretch upstream of the 3% splice site of the ninth intron, were identified as mutations potentially responsible for the alternative skipping of exons 9, 10 and 11 of the goat CSN1S1 F allele. Though the deletion inside the ninth exon was confirmed by means of polymerase chain reaction (PCR) amplification with allele specific primers, no method for identification of the insertions: deletions of the ninth intron has been proposed. The aim of the present study was to develop a method for a simultaneous typing for the deletion at the ninth exon and the 11-bp insertion in the downstream intron.