Fig. 2. Double Helical Structure 

 of DNA (Watson and Crick Mo- 

 del). 



Enzymatic approach to the problem of DNA replication. 

 Although we have in the Watson and Crick proposal a mechanical model 

 of replication, we may at this point pose the question: "What is the chemical 

 mechanism by which this super molecule is built up in the cell?" Some sixty 

 years ago the alcoholic fermentation of sugar by a yeast cell was a "vital" 

 process inseparable from the living cell, but through the Buchner discovery 

 of fermentation in extracts and the march of enzymology during the first half 

 of this century we understand fermentation by yeast as a, now familiar, 

 sequence of integrated chemical reactions. Five years ago the synthesis of 

 DNA was also regarded as a "vital" process. Some people considered it useful 

 for biochemists to examine the combustion chambers of the cell, but tampering 

 with the very genetic apparatus itself would surely produce nothing but dis- 

 order. These gloomy predictions were not justified then nor are similar pessi- 

 mistic attitudes justified now with regard to the problems of cellular structure 



s-52 



