Biopolymers and cell. 2002; 18 (3): 205 - 218

The nature and possible mechanisms of potential mutations formation due to the appearance of tymine dimers after irradiating two-stranded DNA by ultra-violet light

H. A. Grebneva

Mutagenesis caused by UV radiation has been proposed. The main damages resulting in transitions, transversions, frameshift mu¬tations and complex mutations are supposed to be the changes in tautomeric state of the bases affecting their pairing. A model of demoting these rare tautomeric base forms is proposed and grounded for the UV-irradiated DNA. Strong generation of os¬cillations at thermal deexcitation of DNA, absorbing UV-quantum from the triplet electron energy level, causes the changes in length of hydrogen bonds between the bases. Such changes can occur in the base pairs forming dimmers of the cyclobutane pyrimidine type, as well as in the pairs of bases which are not a part of the dinner. We consider the dimers as mutations only when tautomeric state of the bases is changed. It is one of the basic differences between the model proposed and that generally used, according to which all the dimers are supposed to be identical and only DNA-polymerase is sometimes mistaken, including uncomplementary bases into DNA randomly.