Figure 4. The codon size reduction hypothesis of the triplet genetic code origin.

The model considers the possibility that initially dipeptide molecules in the RNA World were synthesized via peptidyl transfer between two interacting amino acid synthesizing ribozymes (shown as squares with attached letter symbols). Such encoding could be used to encode long polypeptides containing short amino acid repeats. A misfolded form of a ribozyme containing regions of complementarity to other ribozymes could be used as a template for the association of other ribozymes. Their combination and ligation would lead to the formation of longer templates capable of encoding a variety of complex protein molecules. The highlighted area of the scheme shows gradual reduction in the size of complementary interactions, a process modeled in the computer simulations described in this work.