A Mendelian polymorphism underlying quantitative variations of goat &alpha; s1 -casein F. GROSCLAUDE, Marie-Françoise MAHÉ, Ghislaine BRIGNON Liliana DI STASIO R. JEUNET l.N.R.A., Laboratoire de Genetique Biochimigue, Centre de Jouy-en-Josas, F 78350 Jouy-en-Josas * /.!V.!.!4., Laboratoire de Biochimie et Technologie Laitieres, Centre de Jouy-en-Josas, F 78350 Jouy-en-Josas ** Osservatorio di Genetica Animale, Via Pastrengo, 28, 10128 Torino, Italie * * l. N. R. A., Station Experimentale Laitiere, B.P. 94, F 39800 Poligny Summary Using SDS-polyacrylamide gel electrophoresis and rocket immunoelectrophoresis, 3 new alle- les, designated a,,-Cn’-, &alpha; s1 -Cn F and &alpha; s1 -Cn o , were identified at the goat a!-Cn locus, in addition 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 ( Y ,,-Cn’ with a low content (0.6 g/I) and a,,- 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, i -Cn° = 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 ; < 2 ,j-Cn<’ = 0 ; a ’I -CnB- = 0.41 ; a,,- Cn’ ! 0.43 ; <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 ’I -Cn 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 words : Goat, < 2 ,j-casein, <2,!-casein, polymorphism, null type, genetic linkage, quantitative variations. Résumé Un polymorphisme mendélien sous-jacent aux variations quantitatives de la caséine a,, caprine A l’aide d’électrophorèses en gel de polyacrylamide SDS et d’immuno-électrophorèses « roc- ket », 3 allèles, appelés <2,j-Cn! , ot,,-Cn’ et a,,-Cn o , ont été identifiées au locus a,,-Cn de la chèvre, en plus des allèles <2,j-Cn!, a,,-Cn° et a,,-Cn’" déjà détectés par BOULANGER et al. (1984). Les allèles <2,j-Cn!, a,,-Cn B et <2,j-Cn! sont associés à un taux élevé de caséine a,, (contribution approximative de chaque allèle : 3,6 g/1), l’allèle a,,-Cn’’ a un taux faible (0,6 g/1) et l’allèle a,,-