22 



MATHICK ,T. nKSSiMAN 



H,C O 



Poly- 

 nucleotide 



H,C 



O— P— O— P— O— P-O 



I /- 



o o 



-XTP 



Yic. 6. Postulated mechanism for extending a DNA chain. (From Kornberg, 

 I960.) 



