The general Lifshitz theory of van der Waals interaction was used to formulate and compute energies between the nucleotides situated on the opposite ends of a broken DNA helix. Our calculation show that infrared and ultraviolet resonances in the dielectric functions of DNA and the intracellular liquid account for less then 10 percent of the forces of interaction, at a range of 5-15 angstroms, between nucleotides. Thus the fundamental contribution to the interaction is presented by the group of resonances with frequencies of X - ray range. It was shown that during the interaction between thymine - guanine, adenine - guanine and cytosine - guanine there exists a potential barrier which prevents DNA selfrepairing after a mutanous, over a distance of about 7 - 20 angstroms, at the room temperature and with reference to the viscosity factor for pure water. All the remaining pairs of nucleotides have no such barrier. In addition the barrier vanishes and DNA undergoes complete selfrepairing with the decreace in viscosity of intracellular medium.