Factors and mechanisms of spontaneous mutagenesis

The present-day views on the mechanism of the mutation occurrence and the nature of the factors of spontaneous mutagenesis were generalized in this paper. According to the theory of a mutation process there stages of the formation of mutations are classified: the formation of primary molecular damages in a chromosome, the occurrence of a pre-mutation state as a result of a change in the DNA structure, the fixation of a potential change into mutation. Primary DNA damages occur spontaneously as a result of a natural chemical instability of DNA molecules; they also may occur under the effect of exo- or endogenous factors of physical, chemical and biological nature. The basis for substantiating the nature of the occurrence of spontaneous gene mutations is the tautomeric hypothesis of Watson and Crick, ionization mechanisms, and the possibility of the occurrence of incorrect pairs of nitrogenous bases of the DNA molecule in the basic, canonical tautomeric form as a source of hereditary variability. The non-coding nucleotide sequences, the mobile genetic elements of different classes, the consequences which correspond to small RNA and the ones which can activate as a result of abrupt changes in the environment or inner environment and can lead to a fast increase of the frequency and expansion of a mutation spectrum – all this was involved into the structural driving forces and the control systems of genomic rearrangements.