Size and shape of mycoplasma virus MV-Lg-L 172 DNA

Sedimentation of DNA of mycoplasma virus MV-Lg-L 172 in neutral and alkaline density gradients showed that the chromosome of this virus is most probably formed by a double-stranded circular DNA molecule with a molecular weight of approx. 10(7) daltons. These results were confirmed by direct electron microscopy of the viral DNA. Gamma-irradiation of the virus caused in its DNA single breaks on the average per each 66 eV of absorbed energy. Virus survival depended exponentially on the irradiation dose, D0 being between 60,000 and 70,000 rads. This dose induced on the average one single break in the DNA.