164 NUCLEIC ACIDS, DECODING, ETC. 



physics, and the biology of the nucleic acids, and even more so 

 in what might be called their metabiology or, perhaps better, 

 their parabiology: a field that could best be described as the 

 borderline between genetics and mythology. Some of the alle- 

 gorical paintings illustrating our views of the role of the nucleic 

 acids compare favorably with the products of the minor masters 

 of the rococo. 



Perhaps the first advance that was made in the chemistry of 

 the nucleic acids was the elaboration of sufficiently precise micro- 

 methods that permitted the quantitative analysis of very small 

 amounts. This was accomplished between 1946 and 1948 and it 

 truly formed the basis of all later work; for it served to demon- 

 strate the existence of a very large number of different nucleic 

 acids and did away with the old tetranucleotide hypothesis. But 

 before going on, I should pause for a moment and remember the 

 names of those that came before, names that our time — long in 

 bibliography, but short in memory — likes to forget: Miescher, 

 Hoppe-Seyler, Piccard, Kossel, Altmann, Neumann, Jones, Steu- 

 del, Feulgen, P. A. Levene, Thannhauser, Hammarsten, Jorpes, 

 Gerhard Schmidt, and Dische. Great work was done by them and 

 by others, and even without the time-saving expedient of silly 

 abbreviations. 



The next thing that the chemical investigation of the nucleic 

 acids accomplished was to demonstrate the species specificity of 

 DNA, i.e., to show that the DNA of a given species had a 

 characteristic and unchanging nucleotide composition; a com- 

 position that appeared to be characteristic of the species, but not 

 of any particular organ. And the third thing was the observation 

 made in 1949 that there existed in all DNA specimens very 

 pecuUar base-pairing regularities. These observations, together 

 with the X-ray studies four years later, had as a direct conse- 

 quence the formulation of DNA as a regularly paired double 

 structure. 



Many of you will undoubtedly be aware of the numerous 

 speculations about the GC content of DNA and its meaning for 

 the physical and biological properties of the polymer, but few 



