Protein synthesis directed by DNA phage messengers.

Even through the amino acids corresponding to most of the 64 nucleotide triplets are now known, several important aspects of the genetic code are not yet fully understood. In particular we need more knowledge about the "punctuation marks" of the code-for example, the signals necessary for the initiation or termination of polypeptide synthesis. One approach to the identification of these signals has been provided by the development of cell-free amino acid incorporating systems directed by natural occurring messenger RNA molecules.