Restriction fragment length polymorphism identification of goat αs1-casein alleles: a potential tool in selection of individuals carrying alleles associated with a high level protein synthesis

The extensive polymorphism of caprine alpha s1-casein, which is controlled by at least seven autosomal alleles segregating in a Mendelian fashion, was investigated by RFLP analysis. Genomic DNA from 77 lactating goats, whose genotypes had been previously determined by electrophoretic analysis of milk proteins, was digested with 11 restriction endonucleases and Southern blots were probed with a radiolabelled ovine alpha s1-casein cDNA. Three enzymes, PstI, TaqI and Rsa I, allowed the unambiguous identification of known alleles alpha s1-CnA, E and O and of the allelic pairs alpha s1-CnD and F] and alpha s1-CnB and C]. Evidence for a second null allele, termed alpha s1-CnO', and for an additional allele, designated alpha s1-CnF', was provided, which leads to the identification of nine alleles at the alpha s1-Cn locus, in this species. Although only 15 out of the 45 expected genotypes could be fully ascertained, this procedure allows the identification at birth of animals carrying the alpha s1-CnA, B or C alleles associated with a high alpha s1- and whole-casein content.