CHAPTER 27 



The Biological Role of the Deoxypentose Nucleic Acids 

 ROLLIN D. HOTCHKISS 



Page 



I. Deoxypentose Nucleic Acids as Genetic Determinants 435 



1. Organization of DNA in Genetic Elements of Tissues 436 



a. Localization of DNA within the Cell 436 



b. Localization of Genetic Determinants within the Cell 437 



c. Quantitative Cytochemical Regularities in DNA Distribution . . . 438 



2. Evidences of Genetic Functioning of DNA 439 



a. Mutational Effects by Agents Reacting with DNA 439 



b. Bacterial Transformations — Observed Genetic Action of Isolated DNA 443 



c. Chemical Nature of Bacterial Transforming Agents 444 



(1) Recognition of DNA Nature 445 



(2) Evidence that Other Substances are not Present 446 



d. Instances of Bacterial Transformation by DNA 447 



e. Biological Nature of Transformation 449 



(1) Parallels between Genes and Transforming Agents 449 



(2) Mutations in Bacteria 450 



(3) Transformations as Stepwise Transfer of a Mutation Pattern . . . 451 



(4) Transforming Agents as Genes 453 



3. Implications of a Genetic Role — Biological Specificity of DNA 454 



a. Specificity in Chemical Composition or Configuration 454 



b. Physical Evidence of Heterogeneity of DNA 456 



II. Deoxypentose Nucleic Acids in Growth and Metabolism 456 



1. Metabolic Stability of DNA 457 



a. DNA Content of Tissues 458 



b. DNA as a Measure of Growth 459 



2. The Significant Role of DNA in Bacteriophage 460 



a. Composition of the T Phages 460 



b. Life Cycle of Virulent Phage— Role of the Protein and DNA 461 



c. Genetic Aspects of Phage Reproduction 464 



d. Origin and Fate of Phage DNA 466 



e. Symbiotic Phages and Other Viruses 467 



f. Transduction — A Transformation Mediated by Phage 468 



III. Other Aspects of DNA Function 469 



1. Other than Genetic Roles for DNA 470 



IV. Summary — Infection, Heredity, and Infectious Heredity 473 



I. Deoxypentose Nucleic Acids as Genetic Determinants 



The possibility that the deoxynucleic acids, in the form of chromatin, 

 have a role in genetic mechanisms has been suggested implicitly, and 



435 



