[Mechanisms ensuring the resistance of the genetic material of the cell to stress exposures]. / Mekhanizmy, obespechivaiushchie ustoichivost' geneticheskogo materiala kletki k stressovym vozdeistviiam.

A brief review of studies performed in the Department of Genetics of St. Petersburg University by M.E. Lobashev and his disciples is presented. The results of these studies prove that the formation of a mutation is a multistage process involving many cell and organism systems (including repair systems, systems that determine sexual dimorphism, etc.), which are affected by environmental factors (e.g., extreme temperatures). They can hinder or accelerate the mutational process, in this way providing both a superadditive effect and adaptive response. Recent studies deal with a universal system of heat shock proteins, which is involved in the maintenance of resistance of genetic material and genetic processes in the cell.

[Analysis of the frequency of spontaneous and induced autosomal recessive lethal mutations in the oogenesis of the radiosensitive mutant rad(2)201G1 of Drosophila melanogaster]. / Analiz chastoty spontannykh i indutsirovannykh autosomnykh retsessivnykh letal'nykh mutatsii v oogeneze radiochuvstvitel'nogo mutanta rad(2)201G1 Drosophila melanogaster.

The frequency of spontaneous and gamma-ray induced autosomal recessive lethals has been studied in chromosomes 2 and 3 at different stages of Drosophila melanogaster radiosensitive mutant rad (2) 201G1 oogenesis. The frequency of spontaneous lethals in radiosensitive mutant was higher by the order of magnitude as compared with wild-type flies (9.3 and 0.6%, respectively). Germ cells of radiosensitive mutant were of high mutability at all stages of oogenesis studied. The irradiation of flies by 1.29 x 10(-1) Kl/kg results in decrease of lethals frequency in radiosensitive mutant as compared with the spontaneous level, whereas under irradiation by 7.74 x 10(-2) Kl/kg no change in mutability was revealed.

[Radiosensitivity of somatic cells and imaginal disks of male and female Drosohila]. / Radiochuvstvitel'nost' somaticheskikh kletok i imaginal'nykh diskov samok i samtsov drozofily.

Primary chromosome damages as well as the frequency of spontaneous and X-rays induced chromosome aberrations in Drosophila melanogaster males and females are studied. It is found using cytofluorimetric method that primary chromosome damages in ganglia cells of females and males are the same. In these cells as well as in cells of imaginal discs the frequency of induced chromosome aberrations, except gaps, is considerably higher for females. Ganglia cells of females and males of Drosophila are found not to differ from each other in their proliferation activity. The frequency of morphoses for both sexes is also the same. The assumption is made concerning the role of the non-identical repair in the increased mutability of female somatic cells, which is more intensive in this sex, as well as concerning more intensive identical repair in imaginal discs of females.

[The dynamics of realization of spontaneous dominant lethal mutations during drosophila ontogenesis]. / Izuchenie dinamiki realizatsii spontannykh dominantnykh letal'nykh mutatsii v ontogeneze drozofily

The dynamics of realization of spontaneous dominant lethal mutations (DLM) has been studied in cyclic crosses of 5 strains of Drosophila at 3 developmental stages. The frequency of the DLM realized at the embryonic stage was shown to be determined by the maternal organism. No predominant role of either parent in the realization of DLM at the larval and pupal stages was established. The total frequency of DLM realized at all developmental stages correlated with that of DLM realized at the embryonic stages and was determined by the maternal organism. The maternal effect in the determination of DLM frequency was not related to the shift in the stage of their realization. The DLM frequency at the embryonic stage may serve as a criterion of mutational process in strains since it reflects their genetical structure but its utilization for characterization of hybrid combinations is not expedient as it is mainly determined by the maternal organism.