THE CRYPTOGRAPHIC APPROACH TO THE 

 PROBLEM OF PROTEIN SYNTHESIS 



George Gamow and Martynas Ycas 



University of Colorado and University of New York 



Abstract — The Watson and Crick suggestion concerning the role of DNA in replication, 

 mutation, and protein synthesis requires a coding between the four-letter DNA alphabet and 

 the twenty-letter protein alphabet. An attempt has been made to discover this code by crypto- 

 graphic methods. Various schemes have been worked out but no success obtained at this 

 writing. There is hope that as the number of protein sequences increases this problem will 

 be solved. 



Speaking about information storage and transfer in a living cell, one always likes 

 to compare the cell with a large factory. The cell nucleus is the manager's office, 

 directing the work of the factory, and the chromosomes are the file cabinets in 

 which all blue prints and production plans are stored. The cytoplasm is the 

 plant itself with the workers and machinery carrying out the actual production ; 

 those are, of course, the enzymes catalyzing various biochemical reactions. If 

 something goes wrong with the information stored in the chromosome, the 

 corresponding enzyme will also do a wrong thing. Consider, for example, an 

 enzyme which produces the pigment necessary for color vision. If the particular 

 section of chromosome carrying the directions for producing that pigment is 

 defective, the enzyme will not get the correct instructions, and will not produce 

 the right type of pigment. As a result, the individual will be color blind. 



The materials of chromosomes and of enzymes are chemically different, 

 except that in both cases we deal with long molecular chains formed by the 

 repetition of a comparatively small number of different units. DNA (deoxyribo- 

 nucleic acid), forming the chromosomes, is a sequence o^ four different units 

 or 'bases': namely, adenine, thymine, guanine, and cytosine. For sake of 

 picturesque presentation, we may associate them with four suits of cards: 

 spades, clubs, diamonds and hearts. Each DNA molecule is equivalent to a 

 sequence of cards many thousand units long, and the way in which different 

 suits follow each other contains, in code form, the instructions to the original 

 cell (fertilized ovum) and its descendants to develop into a rosebush, a skunk, 

 or a man. 



The first question is this. How is information which is carried by DNA 

 molecules of the chromosomes duplicated when the cell goes through the process 

 of division? An answer can be given on the basis of the model of DNA proposed 

 about three years ago by J. Watson and F. Crick (1). They started with the 

 fact, first noticed by E. Chargaff (2), that the number of adenines in any 

 given DNA molecule is always equal to the number of thymines, while the 

 number of guanines is always equal to the number of cytosines (3). In the 

 playing card analogy there are as many spades as there are clubs, and as many 

 diamonds as hearts. This suggests that we deal here with a double-stranded 



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