Four-Factor Model Analysis of Thymidine Incorporation into Mouse DNA and the Mechanism of Radiation Effects

Synthesis of DNA is a complex and highly specific process of incorporation of nucleotide bases into appropriate positions along a macromolecular chain. The detailed mechanism of incorporation is not yet known, but the metabolic pathways immediately preceding incorporation have been studied extensively (1). As a basis for analysis of the kinetics of the pathways, Quastler outlined a model scheme involving four parameters, which he termed the four-factor model (2). The elaboration of this model for the specific case of thymidine incorporation into DNA, an attempt to test it experimentally in mice by autoradiographic techniques, and its application to the analysis of radiation effects on thymidine incorporation are presented here.