CHEMISTRY AND VIRAL GROWTH 



whether all organisms have chosen DNA for a genetic material, 

 which might imply that the choice had been made only once. 

 At the present time this seems unlikely, because a number of 

 plant viruses probably lack DNA. Evidently one of the tasks of 

 the plant virologists is to make very sure of this. 



The second question is the following. In an organism that 

 does make use of DNA, is DNA the sole agent of genetic con- 

 tinuity, or is genetic specificity passed from substance to sub- 

 stance like the token in a relay race? The answer to this ques- 

 tion can only be guessed, but one can hope to get it from T2, as 

 I have tried to show. 



More generally, one wonders what connection there can be 

 between the linear molecules that pass from pneumococcus to 

 pneumococcus, or from T2 to its host, and the relatively enor- 

 mous chromosomes of most cells. A similar question puzzled 

 geneticists, of course, long before anything was known about 

 inheritance in bacteria or viruses (68). I think it is doubtful 

 whether T2 can throw any light on this question except, perhaps, 

 by renewing interest in it. 



More specifically, what connection can there be between 

 genetic recombination in T2 and reciprocal crossing-over be- 

 tween chromosomes? Here the answer may be none (60). 

 Not only because the discrepancy in size forbids analogy; also 

 because recombination in T2 does not seem to be reciprocal 

 (39). 



One suspects that in T2 the mechanical and biochemical 

 bases of inheritance are reduced to their simplest terms; indeed, 

 this is what one hopes. If this proves to be true, it will be unfair 

 to complain that information about this organism cannot be 

 applied directly to more complicated ones. 



Conclusion 



In studying viral growth, one necessarily studies many 

 biochemical problems simultaneously. The main ones involve 

 interrelationships among deoxyribonucleic acids, ribonucleic 



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