A Mendelian polymorphism underlying quantitative variations of goat αs1-casein

Abstract

Using SDS-polyacrylamide gel electrophoresis and rocket immunoelectrophoresis, 3 new alle- les, designated a,,-Cn’-, α , were identified at the goat a!-Cn locus, in addition F and α -Cn s1s1 o -Cn to alleles <2,j-Cn!, as!-Cn° and <2,j-Cn! previously reported by B OULANGER et al. (1984). Alleles a,,- Cn’, a,,-Cn’ and <2,j-Cn! are associated with a high content of a,,-casein (approximate mean contribution of each allele being 3.6 g/I) compared to ,,-Cn’ with a low content (0.6 g/I) and a,,- Y ( Cn° with an intermediate content (1.6 g/1) ; a,,-Cn° appears to be a true null allele. In a sample of 213 Alpine females from 49 flocks in West Central France, the frequencies of the 6 alleles = = = = were : <2,j-Cn! 0.14 ; a,,-Cn° 0.05 ; <2,j-Cn! = 0.01 ; ot,,-Cn’ 0.34 ; a,,-Cn F 0.41 ; and = a, -Cn° i 0.05. In a sample of 159 Saanen females from 52 flocks of the same region, the = = = = frequencies were : <2,j-Cn! 0.07 ; <2,j-Cn! 0.06 ; < ,j-Cn <2,j-Cn’" = 0.03. Additional data confirm that loci a, I -Cn and a,,-Cn are closely linked. Preliminary investigations indicated a significant superiority in casein content of milks from goats possessing the allele <2,j-Cn!, as compared to that of milks from goats of genotypes (xs,-Cn F / / = <2,j-Cn! and <2,j-Cn! /a -Cn ’I F and, in a large herd (N 251), a strong correlation was observed = = between the a,,-casein content and the rennet-casein content of milk (r 0.68 ; b 0.64). Key