66 



Information Storage and Neural Control 



DNA in which each base in the RNA is the complement to eacli 

 base in the DNA. For example, the sequence ATGC in DNA 

 would be translated into UACG in the RNA because U, replacing 

 T in RNA but having similar base pairing properties will form a 

 hydrogen-bonded base pair with A, A with T, C with G, and 

 G with C. An enzyme has been found which appears to catalyze 

 this process. Messenger RNA may bind to ribosomal RNA by 

 means of rather general regions of base complementarity. Finally, 

 transfer RNA need only have a base sequence complementary 

 to the messenger RNA base code for its particular amino acid 

 to fulfill its function, since pairing of the complementary bases 

 will correctly position the amino acid. If the DNA sequence AAA 

 codes the amino acid phenylalanine, then the messenger RNA 

 will have the complementary sequence UUU and the transfer 

 RNA for phenylalanine a sequence AAA. The UUU sequence 

 in the messenger RNA will pair with the AAA sequence in the 

 transfer RNA to provide for the insertion of phenylalanine into 

 its genetically determined site in the protein (Fig. 4). The gene 

 DNA and its messenger RNA are equivalent in informational 

 content, since one is a direct translation of the other. 



C 



.((>Ala 



lAirrAiriATA 



t • I I • I 



iu iu iu iu iu i m-pna 



RNA Flare 



Ribosomal 5ur?cxce 



Fig. 4. Hypothetical base pairing scheme for protein synthesis. Poly U is shown 

 in its role of messenger. The poly U chain binds loosely to a segment of ribosomal 

 RNA flaring out from the "protein surface" of the ribosome. Transfer RNA for 

 phenylalanine is presumed to contain an AAA sequence complementary to the 

 UUU of the poly U and therefore "positions" a sequence of phenylalanines for 

 polymerization into polyphenylalanine. 



