Class 1: pAAA, pCCC, pGGG, pTTT
Class 2: pAAC, pAAT, pACA, pACC, pATA, pATT, pCAA, pCAC, pCCA, pCCG, pCGC, pCGG, pGCC, pGCG, pGGC, pGGT, pGTG, pGTT, pTAA, pTAT, pTGG, pTGT, pTTA, pTTG
Class 3: pAAG, pAGA, pAGG, pCCT, pCTC, pCTT, pGAA, pGAG, pGGA, pTCC, pTCT, pTTC
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