Studies on tritiated thymidine incorporation into DNA molecules by electron microscopic autoradiography

The incorporation of tritiated thymidine into DNA molecules was studied by electr.:m microscopic autoradiography. To make autoradiogram in electron microscopic level, DNA was extracted from rat ascites hepatoma (AH 130) cells after in vitro incubation with tritiated thymidine. Extracted DNA samples were rotary shadowed with platinum palladium and covered with emulsion. Silver grains demonstrated on autoradiogram indicated tritiated thymidine to have incorporated into DNA molecules themselves. The incorporation was further confirmed by liquid scintillation counting of TeA soluble and insoluble fractions after DNase or RNase treatment of the DNA preparations.