Directed molecular evolution.

We propose the existence of a relationship of stereochemical complementarity between gene sequences that code for interacting components: nucleic acid-nucleic acid, protein-protein and protein-nucleic acid. Such a relationship would impose evolutionary constraints on the DNA sequences themselves, thus retaining these sequences and governing the direction of the evolutionary process. Therefore, we propose that prebiotic, template-directed autocatalytic synthesis of mutally cognate peptides and polynucleotides resulted in their amplification and evolutionary conservation in contemporary prokaryotic and eukaryotic organisms as a genetic regulatory apparatus. If this proposal is correct, then the relationships between the sequences in DNA coding for these interactions constitute a life code of which the genetic code is only one aspect of the many related interactions encoded in DNA.