33. NUCLEIC ACIDS OF THE BACTERIAL VIRUSES 203 



dues were glucosylated, respectively. As mentioned previously, in experi- 

 ments with DNA from very highly P 32 -labeled phage, mixed with DNA 

 from unlabeled phage, the stars appeared to migrate on the column with 

 fraction A. 



2. Replication 



a. Fate of the Infecting Particle 



The most careful studies of the fate of the components of the infected 

 particle have been made by Hershey and collaborators, 29 ' 61 following ear- 

 lier work by Kozloff and Putnam, 8385 and French et al. 86 In a classic experi- 

 ment 29 Hershey and Chase demonstrated, using P 32 - and S 35 -labeled phage, 

 that upon absorption of the bacteriophage to the host bacterium, the P 32 

 representing the DNA, is "injected" into the bacterium, while a major 

 portion of the S 35 representing the protein, remains external to the bac- 

 terium and can be largely stripped from the bacteria by the action of a 

 blender without effect upon the subsequent development of infection. 



Of the DNA injected into the host cell a fraction can be recovered in the 

 progeny phage after lysis. This fraction is the same when measured by 

 P 32 transfer or by C 14 transfer. 61 All four purine and pyrimidine residues are 

 transferred equally. 61 In early experiments 83 the fraction transferred was 

 of the order of 30%. Successive improvements in technique 61,87 such as 

 the use of highly active stocks, and of conditions favoring rapid adsorption, 

 a minimum of premature lysis, and a minimum of readsorption, have raised 

 the recovery of parental DNA in the progeny phage to approximately 60 %. 

 Most of the remainder can be accounted for and is lost as the result of 

 various "accidents," i.e., failure of about 12% of the phage to inject, 10% 

 loss of DNA by premature lysis before incorporation into mature phage, 

 12 % loss by readsorption of mature phage from premature lysis, etc. 



Only a few experiments have been performed that bear upon the state of the DNA 

 after injection. Ultraviolet irradiation experiments 88 ' 89 suggest that the injected 

 DNA has the same (or slightly less 40 ) cross section for inactivation as when it is in 

 the virus for the first minute or so after injection. After this, with T2, the cross 

 section decreases for complex reasons (vide infra). 



Similarly, gamma-ray inactivation studies 90 indicate that the inactivation cross 



83 F. W. Putnam and L. M. Kozloff, J. Biol. Chem. 182, 243 (1950). 



84 L. M. Kozloff, J. Biol. Chem. 194, 95 (1952). 



85 L. M. Kozloff, Cold Spring Harbor Symposia Quant. Biol. 18, 209 (1953). 



86 R. C. French, A. F. Graham, S. M. Lesley, and C. E. van Rooyen, ./. Bacterial. 

 64, 597 (1952). 



87 J. D. Watson and O. Maal0e, Biochim. et Biophys. Acta 10, 432 (1953). 



88 S. E. Luria and R. Latarjet, J. Bacleriol. 53, 149 (1947). 



89 S. Benzer, J. Bacleriol. 63, 59 (1952). 



90 W. Harm, Virology 5, 337 (1958). 



