Three casein loci, tightly linked on bovine chromosome 6, have been st
udied as haplotypes within families of bulls. The polymorphisms includ
ed in the study were CASAS1 (B, C), CASB (A1, A, A5, B), CASK (A, B, E
) and a microsatellite in intron III of CASK. A new A5 variant of CASB
, caused by a silent mutation in the triplet coding for amino acid 110
, was detected by direct polymerase chain reaction sequencing. Our ana
lysis of 306 sons and 15 sires revealed 10 different casein haplotypes
with a cumulative polymorphic information content (PIC) of 0.78.