DNA 

 (xlO"5) 



12 3 4 5 



2 3 4 5 



Time in minutes 



Fig. 7. The pattern of acid-soluble thymidine utilization by E. coli B. A trace of 

 tritiated thymidine was added to the growth medium of the bacteria, and was 

 rapidly utilized. Cells taken at the intervals indicated were analyzed for their 

 intracellular acid-soluble thymidine. The distribution in each of several components 

 is given. As may be seen, those components which have been shown to represent the 

 major steady state pool constituents, TDP rhamnose, and TDP-X- (both thymidine 

 (iiphospho sugars) do not appear to serve as immediate DNA precursors. The minor 

 pool constituents, TMP, TDP, or TTP, appear to turn over (incorjiorate and lose 

 radioactivity) rapidly as would be expected. (Unpublished data of Dr. R. Okazaki 

 presented here by his kind permission.) 



168 



