Genetic Control of Protein Synthesis 75 



Echols: The work which Nirenberg and Ochoa have done 

 suggests that there may be a degeneracy in the code; i.e., there 

 may be more than one coding unit which specifies a given amino 

 acid. They only use polymers containing uracil, but they have 

 already worked up to nineteen or twenty amino acids. This 

 suggests that there is either a degeneracy in the code or a rather 

 surprising selection for "sense" codes containing uracil. Also, 

 incorporation of at least one amino acid is promoted by polyiners 

 containing different coding units. 



