SUPPLEMENT V 



THE BIOLOGIC SYNTHESIS OF DEOXYRIBONUCLEIC 



ACID 



by 



Arthur Kornberg. 



Nobel Lecture, December n, 1959. 



The knowledge drawn in recent years from studies of bacterial transfor- 

 mation (1) and viral infection of bacterial cells (2, 3) combined with other evi- 

 dence (3), has just about convinced most of us that deoxyribonucleic acid 

 (DNA) is the genetic substance. We shall assume then that it is DNA which 

 not only directs the synthesis of the proteins and the development of the cell 

 but that it must also be the substance which is copied so as to provide for 

 a similar development of the progeny of that cell for many generations. DNA, 

 like a tape recording, carries a message in which there are specific instructions 

 for a job to be done. Also like a tape recording, exact copies can be made 

 from it so that this information can be used again and elsewhere in time 

 and space. 



Are these two functions, the expression of the code (protein synthesis) and 

 the copying of the code (preservation of the race) closely integrated or are 

 they separable? What we have learned from our studies over the past five 

 years and what I shall present is that the replication of DNA can be examined 

 and at least partially understood at the enzymatic level even though the 

 secret of how DNA directs protein synthesis is still locked in the cell. 



DNA structure. 

 First I should like to review very briefly some aspects of DNA structure 

 which are essential for this discussion. Analysis of the composition of samples 

 of DNA from a great variety of sources and by many investigators (4) revealed 

 the remarkable fact that the purine content always equals the pyrimidine 

 content. Among the purines, the adenine content may differ considerably from 

 the guanine, and among the pyrimidines, the thymine from the cytosine. 



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