  In the framework of the crystal basis model of the genetic code, where each
codon is assigned to an irreducible representation of $U_{q \to 0}(sl(2) \oplus
sl(2))$, single base mutation matrices are introduced. The strength of the
mutation is assumed to depend on the "distance" between the codons. Preliminary
general predictions of the model are compared with experimental data, with a
satisfactory agreement.
