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Studies to analyze the genetic processes in natural populations of plants were started on the territory of the East-Ural Radioactive Trace (EURT) in 1962 and in the zone of the Chernobyl accident in May 1986. The main directions of the genetic studies in both radioactive areas were similar: 1) study of the mutation process intensity depending on the dose and dose rate and analysis of dose-effect relationships for different genetic changes (point mutations, chromosome aberrations in mitosis and meiosis) in irradiated plant populations; 2) study of the mutation process dynamics in generations of chronically (prolongly) irradiated populations of plants; 3) analysis of microevolutionary processes in irradiated plant populations. The report presents an analysis of observed dose-effect relationships under the action of radiation on populations of Arabidopsis thaliana, Pinus sylvestris and a number of other plant species. Analysis of the mutation processes dynamics in 8 Arabidopsis populations growing in the zone of the Chernobyl catastrophe has demonstrated that the level of the embryo lethal mutations 10 years after the accident in the irradiated populations significantly exceeds the control level. The following phenomena observed in chronically irradiated populations have also been considered: increased radioresistance of irradiated populations (radioadaptation), the appearance of abnormal karyotypes and selective markers upon chronic irradiation. The authors call attention to the high importance of monitoring of genetic processes in irradiated plant populations for understanding of the action of radiation on human populations.

The frequency of irradiation-induced recessive lethals has been studied in chromosomes 1 and 2 of Drosophila melanogaster. It supposed, that the higher level of mutability may be explained in destabilization of genotype. The essential part in induction of genotype destabilization replies the genome instability mechanisms.

In 1986-1994, genetic effects of radiation on males of wild mice caught in areas of radioactive contamination after the Chernobyl reactor accident were studied. The gamma-radiation dose rates on the soil surface in the areas varied from 0,02 to 200 mR/h. The frequency of reciprocal translocations in mouse spermatocytes was relatively low and increased linearly with increasing of the dose rate. The levels of recessive lethal mutations in mouse populations did not depend on the radiation dose rate in the areas and decreased with a time.

Genetic effects of irradiation in males of wild house mice which were caught in the region of Chernobyl Nuclear Power Station were studied. The dose rate on the ground surface varied from 0.04 to 200 mR/h of gamma-irradiation. The increasing yield of dominant lethal mutations was only observed in males from the most contaminated sector. Reciprocal translocations were observed in spermatocytes of mice at all the levels of contamination. The rate of reciprocal translocations was relatively low and increased linearly with the elevation of the dose rate. The extent of testis damages increased also, as the dose rate grew. The frequency of abnormal sperm heads, the yield of recessive lethal mutations, litter size and radiosensitivity of the first progeny were not changed, depending on the dose rate.