One of explanations of revealed effects of small doses of an irradiation is induced genetic instability on which background there is a realization of the various radiobiological reactions resulting as to stimulation, and significant oppression of the vital functions of a cell or an organism. In work the given estimations of consequences of an irradiation in small doses of mutant lines of the drosophila are submitted. Paramount value in definition of their size and an orientation of reaction of a genotype is supposed, that, have processes leaders to change of activity of mobile genetic elements and programmed destruction of a cell.