The origin of the genetic code.

A new approach to the origin of the genetic code is proposed based on some regularities in the nucleotide distribution pattern of the code. The relative amounts of various amino acids in primitive proteins were possibly different from those in organisms living today. The primordial ratio was supposed to shift to the modern one guided by the action of primitive nucleotides. Each primitive tRNA had a discriminator site and, distinguished from it, an anticodon site. It also postulated that primordially each amino acid could correspond to a wide variety of codons. During the course of the evolutionary change, a selective mechanism worked among the protobionts so that less frequent nucleotides became associated with more abundant amino acids in the primordial conditions,thus finally leading to the present codon catalogue.