  New developments are presented in the framework of the model introduced by
the authors in refs. [1,2] and in which nucleotides as well as codons are
classified in crystal bases of the quantum group U_q(sl(2)+sl(2)) in the limit
q -> 0. An operator which gives the correspondence between the amino-acids and
the codons is now obtained for any known genetic code. The free energy released
by base pairing of dinucleotides as well as the relative hydrophilicity and
hydrophobicity of the dinucleosides are also computed. For the vertebrate
series, a universal behaviour in the ratios of codon usage frequencies is put
in evidence and is shown to fit nicely in our model. Then a first attempt to
represent the mutations relative to the deletion of a pyrimidine by action of a
suitable crystal spinor operator is proposed. Finally recent theoretical
descriptions are reviewed and compared with our model.
