STUDIES OF THE AFTER-EFFECT OF X-RAYS ON THE MUTATION PROCESS

Abstract

The article comprises the experimental data on the combined effect of the x-ray irradiation and of the subsequent temperature treatment on the frequency of mutations and modifications in Drosophila melanogaster. It has been shown that the exposure to high temperature for one hour after the irradiation with x-rays results in a considerable increase of the mutation rate by far exceeding the sum of the effects of separate x-ray and temperature treatments. The frequency of modifications was also increased by the temperature treatment of larvae for 1—3 hours following the irradiation and this increase likewise exceeded the sum of the separateeffects of x-rays and temperature. The problem is discussed of the reversible state of high sensitivity induced by x-rays (called by the author the after-effect of x-rays) in the immature germ- and somatic cells, during which even relatively slight subsequent action of certain environmental factors amplifies considerably both the genetic and the biological effect of irradiation.