[Q62 |. 1). WATSON 



suggest absolutely nothing and excite us no more than something inert like 

 collagen. 

 The finding of the double helix 2 thus brought us not only joy but great 



relief. It was unbelievably interesting and immediately allowed us to make 

 a serious proposal 3 for the mechanism of gene duplication. Furthermore, this 

 replication scheme involved thoroughly understood conventional chemical 

 forces. Previously, some theoretical physicists, among them Pascual Jordan 4 , 

 had proposed that many biological phenomena, particularly gene replica- 

 tion, might be based on still undiscovered long-range forces arising from 

 quantum mechanical resonance interactions. Pauling 5 thoroughly disliked 

 this conjecture and firmly insisted that known short-range forces between 

 complementary surfaces would be the basis of biological replication. 



The establishment of the DNA structure reinforced our belief that Pau- 

 ling's arguments were sound and that long-range forces, or for that matter 

 any form of mysticism, would not be involved in protein synthesis. But for 

 the protein replication problem mere inspection of the DNA structure then 

 gave no immediate bonus. This, however, did not worry us since there was 

 much speculation that RNA, not DNA, was involved in protein synthesis. 



Introduction 



The notion that RNA is involved in protein synthesis goes back over twenty 

 years to the pioneering experiments of Brachet and Caspersson 6 who showed 

 that cells actively synthesizing protein are rich in RNA. Later when radio- 

 active amino acids became available, this conjecture was strengthened by the 

 observation 7 that the cellular site of protein synthesis is the microsomal 

 component, composed in large part of spherical particles rich in RNA. Still 

 later experiments 8 revealed that these ribonuclcoprotcin particles (now con- 

 veniently called ribosomes), not the lipoprotein membranes to which they 

 arc often attached, are the sites where polypeptide bonds are made. Most 

 ribosomes arc found in the cytoplasm and correspondingly most cellular 

 protein synthesis occurs without the direct intervention of the nuclear-lo- 

 cated DNA. The possibility was thus raised that the genetic specificity pres- 

 ent in DNA is first transferred to RNA intermediates which then function 

 as templates controlling assembly of specific amino acids into proteins. 



We became able to state this hypothesis in more precise form when the 

 structure of DNA became known in 1953. We then realized that DNA's 



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