320 WENDELL M. STANLEY 



possessing virus activity. It would now appear necessary to recognize that a 

 nucleic acid structure of around 1,000,000 molecular weight can possess codes 

 within its 3000 or so nucleotides not only all of the information that is necessary 

 to bring about in the host cell the production of more of this same nucleic acid, 

 but also apparently the de novo synthesis of its own characteristic and highly 

 specific protein with which it eventually coats itself. This work provides won- 

 derful evidence for a direct relationship between specific nucleic acid and specific 

 protein synthesis and makes it possible to consider virus and gene action, in- 

 cluding their relationships to the nature of life, in terms, not of nucleoprotein 

 structure, but in terms of nucleic acid structure. We see, most importantly, that 

 viruses, genes and life are all directly dependent upon the structure of nucleic 

 acid. 



It may be calculated that a thousand-unit polynucleotide linear chain consisting 

 of a coded repeat of only four different components, adenine, guanine, cytosine 

 and uracil in the same ratio as exists in tobacco mosaic virus nucleic acid could 

 form about lo^^^o different arrangements. This number is so large that it is 

 incomprehensible. Even a one-hundred-unit polynucleotide chain of this com- 

 position could exist in about lo^'^ different arrangements and this number is vastly 

 larger than the total of all Hving things on earth and in the oceans. We have, 

 therefore, in this structure consisting of the four chemicals, adenine, guanine, 

 cjrtosine and uracil (thymine in the case of deoxyribonucleic acid) repeated many 

 times over in unique fashion the code for every bit of life on earth and in the sea. 



I believe that the elucidation of the structure of nucleic acid in all of its aspects 

 is the most important scientific problem we face to-day. It is vastly more im- 

 portant than any of the problems associated with the structure of the atom, for 

 in nucleic acid structure we are dealing with Ufe itself and with a unique approach 

 for bettering the lot of mankind on earth. It is possible that the solution of this 

 scientific problem could lead eventually to the solution of major political and 

 economic problems. Never before has it been possible to realize so fully our 

 utter dependence upon the structure of nucleic acid. Eventually chemists should 

 be able to synthesize a small polynucleotide specifically arranged, hence one may 

 now dare to think of synthesizing in the laboratory a structure possessing genetic 

 continuity and of all of the tremendous implications of such an accomplishment. 



SELECTED REFERENCES 



O. T. Avery, C. M. MacLeod & M. McCarty, Studies on the chemical nature of the 

 substance inducing transformation of pneumococcal types. Induction of trans- 

 formation by a desoxyribonuclcic acid fraction isolated from pneumococcus 

 type III. J. exp. Med., 79, 137, 1944. 



J. BORDET, Tlie theories of the bacteriophage. Proc. Roy. Soc, B, 107, 398, 193 1. 



Melvin Calvin, Chemical evolution and the origin of life. Amer. Scientist, 44, 248, 

 1956. 



The Nature of Virus Multiplication (Eds. Sir Paul Fildes and W. E. Van Heyningen). 

 Cambridge University Press, 1953. 



H. Fraenkel-Conrat & Robley C. Williams, Reconstitution of active tobacco mosaic 

 virus from its inactive protein and nucleic acid components. Proc. not. Acad. 

 Sei., Wash., 41, 690, 1955. 



H. Fraenkel-Conrat, The role of the nucleic acid in the reconstitution of active tobacco 

 mosaic virus. J. Amer. ehem. Soc, 78, 882, 1956. 



