Class 1: pAAA, pCCC, pGGG, pTTT
Class 2: pAAC, pAAG, pAAT, pACA, pAGA, pATA, pCAC, pCCA, pCCG, pCCT, pCGC, pCTC, pGAG, pGCG, pGGA, pGGC, pGGT, pGTG, pTAT, pTCT, pTGT, pTTA, pTTC, pTTG
Class 3: pACC, pAGG, pATT, pCAA, pCGG, pCTT, pGAA, pGCC, pGTT, pTAA, pTCC, pTGG
Class 4: pACG, pACT, pAGC, pAGT, pATC, pATG, pCAG, pCAT, pCGA, pCGT, pCTA, pCTG, pGAC, pGAT, pGCA, pGCT, pGTA, pGTC, pTAC, pTAG, pTCA, pTCG, pTGA, pTGC