Analysis of defective SV40 DNA by agarose gel electrophoresis

The SV40 DNA that was generated by undiluted passaging of the virus was analysed by agarose gel electrophoresis. Nine bands of virus DNA were distinguished and each band contained a specific size class of DNA, all shorter than the complete SV40 genome as was determined by electron microscopy measurements. A difference of 2% in length, about 100 base pairs, resulted in a clear band splitting. Two sets of undiluted passaging were established and the defective DNA in the two sets had both different and similar size classes varying in length from 96% to 73% of the unit length SV40 DNA.