Chapter III 



The Organization of DNA in 

 Bacteriophage and Bacteria 



CHARLES A. THOMAS, JR. 



The Johns Hopkms University, 

 Baltimore, Maryland 



I. Bacteriophage DNA 113 



A. The Organization of DNA in the Intact Phage Particles . . . . 114 



B. The Structure of the Liberated Phage DNA Molecule .... 121 



C. The Genetic Structure of Phage 131 



D. The Distribution of Parental Phage DNA to Progeny Phage ... 138 

 II. Bacterial DNA 141 



A. Cytology of Bacteria 142 



B. Growth and Transfer Experiments 142 



C. The Structure of DNA Liberated from Bacteria 145 



D. The Genetic Structure of Bacteria 145 



E. Conclusions 148 



Acknowledgments 148 



References 148 



I. Bacteriophage DNA 



The extensive development of the field of bacteriophage genetics has led 

 to an increasing interest in the structure and organization of bacterio- 

 phage DNA. Since bacteriophage are the smallest biological units which 

 are susceptible to thorough genetic analysis, and since their DNA is 

 best described in molecular or chemical terms, a better understanding 

 of the structure of phage DNA promises to lead to a chemical interpreta- 

 tion of genetic recombination, replication, and transcription. In addition 

 to the genetic functions of DNA, this molecule has the important ability 

 to assume a folded, compact configuration such as found in chromosomes, 

 spores, and sperm heads. A form of this tertiary structure of DNA is 

 found in the compact arrangement of the DNA inside bacteriophage. One 

 may hope that the study of the organization of DNA in the phage head 

 will lead to an understanding of the principles and requirements of this 

 folding process. 



It is convenient to divide these studies into those performcMl on the 

 intact virus particles, and those on the liberated DNA molecules. 



113 



