By means of semi-empirical quantum chemical calculations (AMI) it was first established that a single profanation of DNA bases, that doesn't disrupt Watson-Crick base pairing, substantially changed their tautomeric equilibrium in both directions depending on a profanation site. The profanation of N3 Ade, O6 and N7 Gua, O2 Cyt and O4 Thy atoms stabilizes the canonical tautomeric form, while the high-energy non-canonical tautomers (iminic Ade and enolic Gua) are stabilized by the profanation of N7 Ade, N3 Gua and O2 Thy atoms. The stabilization of DNA base canonical tautomers by selected profanation with the Lys, Arg and His side chains was supposed to be used by DNA-polymerase in DNA synthesis to minimize spontaneous mismatches caused by prototropic tautomerism of the bases at the stage previous to their pairing in polymerase sites for matched pairs recognition.