the present work is devoted to describe a set of rules explaining the discriminating versus non-discriminating behavior of the di-basic stages and to characterize the role of each base in determining such a behavior. Bases are analyze as dual entities characterized by its chemical type and the number of H bonds involved in the codon-anticodon interaction. A codon is characterized as an asymmetric informative entity whose global informative capacity results from the spatially organized combinatory of the 6 proper-ties assigned by the 3 bases.