Electron microscopic studies of replicating SV 40 DNA

Electron microscopic observation of replicating SV 40 DNA has revealed the existence of two types of RF, e form and (1 form. The frequency of RF at 54 hours after infection was 8.9% for the e form and 4.3% for the (1 form. Morphological evidence exhibits that in (1 form RF the tails are, predominantly, shorter than the viral genome and double length SV-40 genomes are also capable of replication in SV-40 infected VERO cells.