106 Information Storage and Neural Control 



25S and 16S (see reference 35). The molecular weights of these 

 components are of the order of magnitude of 500,000 and 1,000,000. 

 It was formerly believed that ribosomal-RNA functioned as a 

 template for protein synthesis but recent experiments have cast 

 doubt on this concept (4, 27). Possibly, ribosomal-RNA is inert 

 with respect to genetic coding. Ribosomal-RNA is only slowly 

 synthesized in the cell and the mechanism by which it is synthesized 

 is unknown. There is no obvious relationship between the com- 

 position of either ribosomal-RNA or T-RNA and that of the 

 DNA of a given organism. 



Since ribosomal-RNA comprises the bulk of the RNA of a cell, 

 the nucleotide composition of ribosomal-RNA is similar to that 

 of the total cellular RNA. The mononucleotide compositions of 

 the total RNA of bacteria, algae, higher plants, fungi, protozoa, 

 and higher animals are shown in TABLE XI and those of the 

 ribosomal-RNA of several organisms in Table XII. 



TABLE XII 



% G + G OF RiBOSOMAL RNA 



The molar per cent (G+C) of the total RNA and the ribosomal- 

 RNA of organisms generally increases as the molar per cent 

 (G+C) of the DNA increases. However, the correlation between 

 total RNA and DNx^ composition is rather weak (1) and the 

 change in RNA composition from one species to another is much 

 less than that of the DNA. Belozersky and Spirin (2) have com- 

 piled the RNA nucleotide composition of fifty-five strains of 

 bacteria. Some representative values are shown in Table XI. The 



