Abstract
Electrophoretic analysis of native and denatured RNA of feline leukaemia virus (FeLV) has revealed small but significant size differences between the RNAs of a number of FeLV isolates. The mol. wt. of the denatured or subunit RNA has been estimated to range from 2·2 to 2·6 x 106 in the different isolates, each of which belonged to one or more FeLV subgroups (A, B and C). The RNA of subgroup A virus was smaller than that of subgroup B virus, while the RNA of subgroup C virus appeared to be intermediate in size between the RNAs of A and B subgroup viruses. Size differences were, however, also found between RNAs of FeLV isolates of a single subgroup (A), indicating that no simple relationship exists between RNA size and virus subgroup.