The Repeated Sequences in Serially Passaged SV40 DNA

Three populations of altered SV40 DNA molecules, independently derived by serial passage of plaque-purified virus at high multiplicity of infection, were found to contain reiterated viral sequences, as determined by reassociation kinetic experiments. In each case, the reiterated sequences corresponded to some of those contained in Hin-fragment s C or D, obtained by digesting plaque-purified virus DNA with Hemophilus influenzae restriction endonuclease. It is suggested that the reiteration of sequences in Hin-fragment C, which is known (Danna and Nathans, 1972; Fareed, Ganon, and Salzman, 1972) to contain the origin of SV40 DNA replication, is responsible for the advantageous replication rate of altered viral genomes during serial passage.