302 ERWIN CHARGAFF 



be made to a recent discussion from our laboratory [lo] in which an attempt was 

 made to relate the one general regularity of both DNA and PNA, namely, the 

 presence of equal numbers of 6-amino and 6-keto nucleotides, to the one 

 regtilarity common to all proteins, the regular occurrence of peptide hnkages. 

 A detailed inquiry into the mechanism of this conjunction of protein and 

 nucleic acid, let alone the construction of a reasonable model or the attempt at 

 uiuravelling the information code of the cell, is premature; for no truly homo- 

 geneous nucleoprotein has yet been discovered of which it could be said that 

 the particular nucleic acid molecule contained in it, with its unique nucleotide 

 sequence, has given rise to the particular protein, with its equally unique amino 

 acid sequence, or vice versa. In other words, we are still lacking the Rosetta 

 stone of biochemistry. 



It is not profitable to speculate on the direction in which the ancestral roles 

 of the nucleic acids could be approached. But it can be predicted that further 

 investigations along the following lines will be of value : (a) virus nucleoproteins ; 

 (b) mechanism of enzyme induction; (c) mechanism of antibody production; 

 (d) role of priming substances in the enzymic synthesis of high polymers. 



REFERENCES 



1. E. Chargaff, Experientia, 6, 201, 1950. 



2. E. Chargaff, in The Nucleic Acids. (Ed. by E. Chargaff & J. N. Davidson), 



Academic Press, New York, Vol. I, p. 307, 1955. 



3. B. R. D. HOTCHKiss, in The Nucleic Acids, 2, 435, 1955. 



4. J. Brächet, in The Nucleic Acids, 2, 475, 1955. 



5. E. Chargaff, in Essays in Biochemistry. New York, 1956. 



6. A. Rosenberg & E. Chargaff, Biochim. biophys. Acta, 21, 588, 1956. 



7. E. Chargaff & R. Lipshitz, J. Amer. ehem. Soc, 75, 3658, 1953. 



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p. 41, 1952. 



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I77> 405, 1949- 



13. E. Chargaff, C. F. Crampton & R. Lipshitz, Nature, Lond., 172, 289, 1953. 



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15. H. S. Shapiro & E. Chargaff, Biochim. biophys. Acta, 23, 451, 1957. 



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