112 Information Storage and Neural Control 



zone electrophoresis in starch columns and centrifugation in 

 sucrose gradients. T-2 specific RNA had a higher electrophoretic 

 mobility and a greater heterogeneity in size than the principal 

 normal RNA components. The T-2 specific RNA was found to 

 be bound to the ribosomes, but with a linkage very sensitive to 

 disruption by low magnesium levels. 



Renaturation and hybrid formation experiments were per- 

 formed to establish that sequence complementarity existed be- 

 tween "T-2 phage specific RNA'' and T-2 phage DNA (28). 

 RNA-DNA complex formation was demonstrated in mixtures of 

 heat denatured T-2 phage DNA and purified T-2 RNA subjected 

 to the slow cooling process. The success of the hybridization 

 experiments suggested immediately that the original observation 

 by Volkin and Astrachan (76) of a similarity in base composition 

 between T-2 RNA and DNA was indeed a reflection of a more 

 profound homology. Hybrid formation was specific. Heterologous 

 DNA from Psendomonas aeruginosa, E. coli, or phage T-5 did not 

 yield DNA-RNA hybrids with T-2 RNA. This led to the con- 

 clusion that the nucleotide sequences of T-2 DNA and RNA 

 were complementary. 



In further experiments Spiegelman, Hall, and Storck (68) 

 demonstrated the natural occurrence of DNx\-RNA hybrids in 

 phage infected E. coli cells. Finally, Hayashi and Spiegelman (29) 

 and Gros et at. (27) have demonstrated the presence of natural 

 DNA-RNA hybrids in uninfected bacterial cells. 



THE GENETIC CODE 



The recent experiments of Nirenberg and Matthaei (48) and 

 of Ochoa and collaborators (42, 67) represent a major break- 

 through and give promise of providing the key to the entire 

 genetic code within one or two years. Nirenberg and Matthaei (48) 

 were able to develop a cell free ribosomal system from E. coli in 

 which the amount of incorporation of amino acids into proteins 

 was dependent upon the addition of heat stable RNA preparations. 

 Transfer-RNA could not replace the active RNA fraction which 

 presumably contained some messenger-RNA. 



Of particular interest was the most important observation that 

 the addition of a synthetic polyribonucleotide, polyuridylic acid. 



