Purpose To study the effect of microwave (MW) irradiation and consistent action of microwaves and static magnetic field (MF) on the giant chromosomes endoreduplication in Drosophila melanogaster Meig. Materials and methods Experiments were carried out on inbred wild type Canton-S strain. Exposure to microwaves (frequency - 36.64 GHz, power density - 1 W/m(2), exposure time - 30 sec) and static magnetic field (intensity - 25 mT, exposure time - 5 min) applied at the egg stage after a 2-h oviposition. Giant chromosomes were investigated in squashed preparations of the salivary glands stained by acetoorcein by the cytomorphometric method. Preparations were obtained from Drosophila larvae at the 0 h prepupae stage. Results Exposure to microwaves increased the degree of polyteny in chromosomes (DPC) by 7.5%, and the statistical power of the impact was: h(2) = 35.3%. A similar effect occurred after the sequential action of microwaves and static magnetic field: The polyteny level of chromosomes increased by 7.4%, statistical power was: h(2) = 30.6%. Conclusions Exposure to microwaves on the stage of embryogenesis has a stimulating effect on endoreduplication in Drosophila development. The effect of microwaves was not modified by the action of the static magnetic field.
The influence of electromagnetic field exposure on puffing pattern of salivary gland polythene chromosomes, viability and fertility of Drosophila melanogaster of the wild type Canton-S line was studied. Experimental conditions: Electromagnetic field characteristics: frequency — 36.64 GHz, power density — 0.4 W/m2, exposure time −10 seconds. Electromagnetic field exposure was conducted on the egg stage. Results: in larvae developed from the exposed eggs 3 of 8 chromosomal puffs tested (71CE, 82EF, and 83E) had significantly smaller dimensions than these in control at the prepupal stage. Viability of Drosophila estimated by the number of adult flies hatched from exposed eggs decreased, while the number of dominant lethal mutations increased. Conclusion: the exposure to a low-level microwave irradiation suppressed puffing activity at ecdysone-inducible loci of Drosophila polythene chromosomes, increased frequency of dominant lethal mutations and decreased Drosophila viability but did not influence Drosophila fertility.
Polyteny is an effective mechanism for accelerating growth and enhancing gene expression in eukaryotes. The purpose of investigation was to study the genetic variability of polyteny degree of giant chromosomes in the salivary glands of Drosophila melanogaster Meig. in relation to the differential tness of different genotypes. 16 strains, lines and hybrids of fruit ies were studied. This study demonstrates the signi cant in uence of hereditary factors on the level of polytenization of giant chromosomes in Drosophila. This is manifested in the differences between strains and lines, the effect of inbreeding, chromosome isogenization, hybridization, adaptively signi cant selection, sexual differences, and varying degrees of individual variability of a trait in different strains, lines, and hybrids. The effect size of the genotype on the degree of chromosome polyteny in Drosophila salivary glands was 45.3%, the effect size of sex was 9.5%. The data obtained allow us to conclude that the variations in the level of polyteny should be considered as a manifestation of the structural and functional polymorphism of giant chromosomes, which is an essential factor in the differential tness of ies and has a selective value.
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