RESUMO
This paper describes the observation of a direct relationship between the absorbed doses of neutrons and the frequencies of somatic mutation and recombination using the wing somatic mutation and recombination test (SMART) of Drosophila melanogaster. This test was used for evaluating the biological effects induced by neutrons from the Triga Mark III reactor of Mexico. Two different reactor power levels were used, 300 and 1000 kW, and two absorbed doses were tested for each power level: 1.6 and 3.2 Gy for 300 kW and 0.84 and 1.7 Gy for 1000 kW. A linear relationship was observed between the absorbed dose and the somatic mutation and recombination frequencies. Furthermore, these frequencies were dependent on larval age: In 96-h-old larvae, the frequencies were increased considerably but the sizes of the spots were smaller than in 72-h-old larvae. The analysis of the balancer-heterozygous progeny showed a linear absorbed dose- response relationship, although the responses were clearly lower than found in the marker-trans-heterozygous flies. Approximately 65% of the genotoxicity observed is due to recombinational events. The results of the study indicate that thermal and fast neutrons are both mutagenic and recombinagenic in the D. melanogaster wing SMART, and that the frequencies are dependent on neutron dose, reactor power, and the age of the treated larvae.
Assuntos
Mutação , Nêutrons/efeitos adversos , Recombinação Genética , Animais , Relação Dose-Resposta à Radiação , Drosophila melanogasterRESUMO
A method to obtain the absorbed dose in Drosophila melanogaster irradiated in the thermal column facility of the Triga Mark III Reactor has been developed. The method is based on the measurements of neutron activation of gold foils produced by neutron capture to obtain the neutron fluxes. These fluxes, combined with the calculations of kinetic energy released per unit mass, enables one to obtain the absorbed doses in Drosophila melanogaster.