Nucleic Acids as Carriers of Biological 

 Information 



ERWIN CHARGAFF 



Columbia University , New York, U.S.A. 



IS THERE A HIERARCHY OF CELLULAR 

 CONSTITUENTS ? 



Our time is probably the first in which mythology has penetrated to the mole- 

 cular level. I read, for instance, in a recent article by a very distinguished biologist : 



' ... In the early phases of the molecular stage of evolution, only simple 

 molecules were formed. . . . Later more complex molecules, such as amino acids 

 and perhaps simple peptides, were formed. 



'In the more advanced phases of this period it is believed that there appeared 

 a molecule with two entirely new properties : the ability systematically to direct 

 the formation of copies of itself from an array of simpler building blocks, and 

 the property of acquiring new chemical configurations without loss of abuity to 

 reproduce. These properties, self-duplication and mutation, are characteristic 

 of all living systems and they may therefore be said to provide an objective basis 

 for defining the Uving state. 



'Evidence is accumulating that the nucleic acids of present-day organisms 

 possess these two properties, and it is perhaps no longer useless to speculate 

 that the first "hving" molecule might have been a simple nucleic acid, perhaps 

 protected by an associated simple protein. . . . ' 



Thus, what started cosmically with beautiful and profound legends has come 

 down to a so-called 'macromolecule'. If poetry has suffered, precision has not 

 gained. For we may ask whether a model that merely provides for one cell 

 constituent continually to make itself can teach us much about life and its 

 origins. We may also ask whether the postulation of a hierarchy of cellular 

 constituents, in which the nucleic acids are elevated to a patriarchal role in the 

 creation of Uving matter, is justified. I beheve there is not sufficient evidence 

 for so singling out this particular class of substances. 



We know that autarkic entities (cells and cell communities) require the pre- 

 sence of a very large number of different compounds, foremost among which 

 are the ubiquitous plastic constituents, namely: (i) Nucleic acids (both of the 

 deoxypentose and pentose types, DNA and PNA); (2) proteins; (3) lipids; 



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