HO.CH, 



OH 



HO.CH 



OH OH 



D-Ribose 



OH 



(2-6) 



OH H 



2-Deoxy-D-ribose 



the purines are adenine and guanine (Formula (2-7)). In so far as the 

 bases are concerned, the only difference between the two kinds of nucleic 

 acids is that thymine is found as a component only in DNA. Uracil ap- 

 pears to be confined exclusively to RNA. As to distribution in the cell, 

 DNA appears to be specifically associated with the chromosomes while 

 RNA is found in the nucleolus, chromosomes, and cytoplasm. Although 



OH 



NH. 



c 



N 



I 

 HO— C2 



CH 



II 

 CH 



N 

 Cytosine 



CH 



II 

 CH 



NH, 



C 



N 



HC 



^^ 



N 



N 



N 

 H 



Adenine 



OH 



CH 



C 



N 



I 

 HaN— C 2 



N 



C 



II 



c 



N 



N 

 H 



Guanine 



(2-7) 



CH 



the role of nucleic acid in cell metabolism is not completely known, 

 there are some general relationships which are now accepted rather 

 widely. There apparently is a relatively clear-cut relationship between 

 DNA and sites of "genetic information." The strongest direct evidence 

 for this is the fact that in some strains of bacteria it has been clearly 

 shown that highly purified DNA can transmit genetic material. RNA 

 appears to be intimately associated with protein synthesis but exactly 

 what this relationship is has yet to be determined (see Chapter 4 for 



GENERAL MORPHOLOGY AND CHEMISTRY OF THE CELL / 17 



