An allele associated with a non-detectable amount of alpha s2 casein in goat milk.
The goat CSN1S2 locus is characterized by the presence of three alleles, A, B and C, all associated with about 2.5 g/l of protein per allele. The SDS-PAGE analysis of 441 individual milk samples obtained from goats belonging to a population reared in Southern Italy showed that the milk produced by three goats did not apparently contain alpha s2-casein, whereas milk produced by 37 goats showed a less intense electrophoretic band of this casein fraction (about 50%). These results can be explained by hypothesizing the presence of another allele at this locus, CSN1S2o, associated with a 'null' content of alpha s2-casein. Southern blot, PCR and PCR-RFLP analyses of the DNA region containing the CSN1S2 gene of individuals producing milk with and without alpha s2-casein did not show differences between the two groups. As a consequence, goats producing milk without alpha s2-casein carry an apparently intact gene. The first results obtained by sequencing part of the CSN1S2o allele revealed a G-->A transition at nucleotide 80 of the 11th exon which creates a stop codon and could be responsible for the absence of the alpha s2-casein in goat milk. This mutation eliminates a NcoI restriction site. A test based on this polymorphism has been established in order to identify carriers of the CSN1S2o allele.
Ramunno
L
L
Dipartimento di Scienze Zootecniche e Ispezione degli Alimenti, Università degli Studi di Napoli Federico II, Via Università 133, 80055 Portici, Na., Italy. ramunno@unina.it
Longobardi
E
E
Pappalardo
M
M
Rando
A
A
Di Gregorio
P
P
Cosenza
G
G
Mariani
P
P
Pastore
N
N
Masina
P
P
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D002364:Caseins / Q000235:genetics* / Q000378:metabolism; D018388:Codon, Terminator; D004247:DNA / Q000235:genetics; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D006041:Goats / Q000235:genetics*; D010446:Peptide Fragments / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length
D002364:Caseins; D018388:Codon, Terminator; D017931:DNA Primers; D010446:Peptide Fragments; D004247:DNA