ROLE OF NUCLEIC ACIDS 



ADENINE ADENINE THYMINE 



81 



ADENINE 

 CYTOSiNE / GUANINE 



CYTOSiNE 



, Guanine 



(a) According to Stent (1958). 



^(23"), 



'0--' \(Rl 



/Guoniney--^' „*.- N> 



(DNA)r ^elix ^ 



>H \IV2i0A 



. :.A^ r/(22'') 



(NHj) 3-OA. ^ / ^ 



/Cytosine 

 IN A)/ 



(b) According to Zubay (1958b). 



Fig. 23. Purine-pyrimidine triplets which may be involved in directing 

 the synthesis of an RNA chain upon a DNA double helLx. 



