ABSTRACT:We introduce a new "modular" (compositional and positional) determinative degree for the four bases U, C, A, and G to define a "Dinucleotide charge number" for the dinucleotides, which discriminates between the two octets of dinucleotides: M 1 and M 2 . These two components are exchanged under a transformation, which, we show, implements the Rumer symmetry. We invoke also the base "size index" of Rosen as a complementary determinative degree for the third-base component of a codon. Next, we define the address functions for the 64 codons (amino acids), which are functions only of the composition and position of these codons in the genetic table. With these ingredients, we build an algebraic classification of the amino acids in the genetic code and some of its nonstandard versions as a preliminary application.