A Genetic Mechanism for ‘Thread Protein’ Polymorphism in Cattle

Abstract

POLYMORPHISM in the ‘thread proteins’ of cattle sera has been described previously¹. Four phenotypes have been found, depending on the presence or absence of one or both of a pair of threadlike zones, presumably proteins, resolved by starch-gel electrophoresis in phosphate buffer. The two zones are well separated, ‘thread protein’ T1 migrating more slowly than the Sα zone, and T2 more rapidly. Individuals with only a T1 zone (phenotype T1) are readily and consistently distinguished from individuals with only a T2 zone (phenotype T2). Samples taken from the same animal at intervals up to 18 months showed the same phenotypes as the initial samples. However, individuals with both T1 and T2 zones (phenotype T1/T2) or neither zone (phenotype T0) are not differentiated consistently, T1/T2 sometimes appearing as T0. Phenotypes T1/T2 and T0, therefore, are best considered as one phenotype (T^*) in practice.