Sum rules of codon usage probabilities
  In the crystal basis model of the genetic code, it is deduced that the sum of usage probabilities of the codons with C and A in the third position for the quartets and/or sextets is independent of the biological species for vertebrates. A comparison with experimental data shows that the prediction is satisfied within about 5 %. 
L. Frappat, A. Sciarrino, P. Sorba