Relationship between molecular length and biological activity of SV40 DNA

The correlation of infectivity to the length of SV 40 DNA by dilute and undiluted passage was described. DNA was extracted from purified virions by Marmur's method, and propagation of virus was done using VERO cells. The infectivity of SV 40 (simian virus 40) ran parallel with the length of its DNA. Undiluted passage caused shortening of DNA and decrease in infectivity, but when these undiluted group was passaged dilutely, length of DNA approached the original length and the infectivity recovered. In undiluted passage group small circular DNAs under 1.0,11_, so far not reported in the SV 40 DNA, were found in low frequency. Replicating form and dimers were also noted from virions and the nuclei of SV 40 infected VERO cells.