33. NUCLEIC ACIDS OF THE BACTERIAL VIRUSES 



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Fig. 4. Effect of chloramphenicol (30 /ug./ml.) on the synthesis of DNA in T2- 

 infected bacteria. Chloramphenicol was added to the culture at various times from 

 to 12 minutes after infection and the curves indicate the effect of increasing delay 

 upon subsequent DNA synthesis. [From J. Tomizawa and S. Sunakawa, J. Gen. 

 Physiol. 39, 553 (1956).] 



obtained at the time of chloramphenicol addition (Fig. 4). These experi- 

 ments demonstrate that DNA replication can take place in the absence of 

 concomitant protein synthesis. 



Interestingly, although under the latter circumstances DNA accumulates 

 in the infected cells, the progressive decrease in the ultraviolet sensitivity 

 of the phage bacterium complex usually observed during the first 11 to 12 

 minutes of infection 88 ' 89 ' m (vide infra) is abruptly halted by the addition 

 of chloramphenicol. This decrease can be resumed upon the removal of the 

 chloramphenicol some minutes later. Thus the decline in ultraviolet sensi- 

 tivity is not simply related to the synthesis of additional DNA but is ap- 

 parently to be associated with processes involving protein synthesis. 



Other modes of inhibition of protein synthesis have yielded similar re- 

 sults. Thus, by the use of analog inhibitors such as 5-methyltryptophan, 99a 



