Chapter IV 



Cellular Control of DNA Biosynthesis 



KARL G. LARK 



Department of Microbiology, 



St. Louis University School of Medicine, 



St. Louis, Missouri 



I. Introduction 153 



A. The DNA Cycle 155 



B. The Level of Biochemical Control 160 



II. Role of DNA Precursors in Controlling DNA Synthesis .... 162 



A. The Direct Measurement of Deoxynucleotides or Precursors 



Thereof and Their Relation to the DNA Cycle 163 



B. The Measurement of Enzj^me Activity Associated with the 



Production of DNA Precursor 170 



III. Role of Protein or RNA Synthesis in Controlling DNA Synthesis . . 173 



IV. The Physical State of DNA as a Factor ControlHng Its Replication . . 180 



A. Is It Necessary for DNA to Exist in a Special Form in Order for It to 



Be Duphcated? 183 



B. Is DNA Synthesis Compatible with Simultaneous RNA S\Tithesis? . 186 



C. Is DNA Structurally Stabihzed within the Cell and Is This a 



Necessary Part of DNA Replication? 188 



D. Is the Replication of DNA Physically Ordered, with Respect to the 



Macromolecule Itself, with a Beginning, a Middle, and an End? . 158 



V. Other Factors Affecting DNA Biosynthesis and the DNA Cycle . . 190 



A. The Localization of DNA Synthesis 190 



B. Variation in the DNA Cycle 191 



C. Effects of Temperature and Radiation on the DNA Cycle . . . 192 



D. The Effect of the Nutrient Environment 194 



E. The Dissociation of the Cell Division Cycle from DNA Synthesis . 197 

 VI. Summary, Conclusion, and Opinions 197 



Acknowledgments 200 



References 200 



I. Introduction 



The biosynthesis of DNA is a distinctive characteristic of cell pro- 

 liferation rather than of the broad span of phenomena commonly- 

 associated with actively functioning cells. Cells which are rapidly 

 metabolizing may often exhibit little or no DNA synthesis, whereas 

 division requires a previous replication of genetic material if competent 

 daughter cells are to be produced. The mechanisms controlling the 



153 



