Couplings of character and of chirality in the origin of the genetic system.

Data from the literature and new data presented here suggest that the genetic system (coding and protein synthesis) is based on relationships of character and structure between amino acids and nucleic acids. Character relationships seem to be anticodonic and structurally the greatest preferences are seen between the heteropair, L-amino acids and D-ribose nucleic acids. However, living systems using the other heteropair must have been equally likely. Homopairing (L-L and D-D) in living systems seems unlikely. Awareness of the heterocoupling of steric forms narrows somewhat the problem of understanding the origin of chirality.