On the Nature of Viruses, Genes and Life 317 



consider the virus with time. Regardless of certain mental restrictions that may 

 differ from person to person, I think there is no escape from the acceptance 

 ultimately of viruses, including the crystaUizable viral nucleoprotein molecules, 

 as hving agents. This must be done because of their abihty to reproduce or to 

 bring about their own repUcation. Certainly the essence of life is the abihty to 

 reproduce, to create a specific order out of disorder by the repetitive formation 

 with time of a specific predetermined pattern and this the viral nucleoprotein 

 molecules can do. 



Of course, it would have been dull indeed if the first-formed hving agent had 

 been restricted to exact dupUcates of itself. The logical reasoning provided in 

 schemes such as those outlined by Oparin, Calvin and others by means of which 

 relatively complex organic substances could have arisen from inorganic matter 

 provides justification for assuming that a chemical structure, perhaps something 

 like nucleic acid, which possessed the abihty to rephcate, did come into being 

 once upon a time. It needed to have happened only once and thereafter without 

 the great phenomenon of mutation it merely would have kept going until it had 

 filled the world with rephcates of this precise structure or until it had exhausted 

 the starting materials. However, Nature has provided a built-in error so that the 

 rephcation process is not perfect and about one in every milhon or so rephcates 

 is shghtly different. This change, which has been of tremendous fundamental 

 importance, we now recognize as mutation and as these errors or differences 

 were accumulated by rephcating structures it became necessary to make formal 

 recognition of them. These differences or markers we now call genes. We do 

 not recognize genes directly but only by differences. Needless to say, some phy- 

 sical structure had to be responsible for the accumulation, preservation, and 

 potential exhibition of these differences and this assembly of genes we call a 

 chromosome. The incorporation of one or more assembhes of genes into a struc- 

 ture possessing a limiting membrane, which we now call a cell, then made 

 possible gene interchanges between these cellular assembhes. This genetic 

 interchange by the fusion of two cells, a sexual process, also represents a phe- 

 nomenon of the greatest fundamental importance for this permitted genetic 

 recombination, a factor that has served to speed up the evolutionary process 

 immeasurably. Therefore, life as we know it to-day is dependent not only upon 

 reproduction but also upon mutation and genetic recombination. 



Now let us consider for a moment the relationships between genes and viruses 

 since we see that both are related to life. Mullet's estimate of the maximum size 

 of a gene would place it just below tobacco mosaic virus, near the middle of the 

 viruses. Both genes and viruses seem to be nucleoproteins and both reproduce 

 only within specific hving cells. Both possess the ability to mutate. Although 

 viruses generaUy reproduce many times within a given cell, some situations are 

 known in which they appear to reproduce only once with each cell division. 

 Genes usually reproduce once with each cell division but here also the rate can 

 be changed, as, for example, in the case of polyploidy resulting from treatment 

 with colchicine. Actually the similarities between genes and viruses are so 

 remarkable that viruses very early were referred to as 'naked genes' or 'genes on 

 the loose'. Three great discoveries, one which began in 1928, another which has 



