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Comparison of mutability induced by gamma radiation and des in Drosophila melanogaster strains selected for resistance
Elena Diehl-FleigI; Edmundo Kanan MarquesII
ILaboratório de Genética, Departamento de Biologia, Universidade do Vale do Rio dos Sinos, Caixa Postal 275, 93020 São Leopoldo, RS, Brasil. Send correspondence to E.D.F.
IIDepartamento de Genética, Universidade Federal do Rio Grande do Sul, Caixa Postal 1953, 90001 Porto Alegre, RS, Brasil
ABSTRACT
In order to verify whether Drosophila melanogaster strains, selected for resistance to induction of recessive lethal mutations of the X chromosome, also are resistant to mutation induction by chemical agents, tests were carried out with gamma rays (4840 R) from 60Co, with DES (0.3, 0.4 and 0.5%) and with joint treatments 60Co (4840 R) and DES (0.4%).
Tests with gamma rays proved that the strains that were selected for radioresistance still keep such a characteristic, 20 generations after stopping selection and irradiations.
DES induced a significantly lower rate of sex-linked recessive lethals in radioresistant strains, when compared to the controls. These results suggest the existence of common repair mechanisms for damage brought about both by physical and chemical agents.
In the joint 60Co and DES treatments, we noticed an increase in the lethal rate, with an almost additive effect in the radioresistant strains; while in the control strain, the lethal rate was similar to that obtained from isolated treatments. Such results suggest that DES partially inhibited or inactivated the repair enzymes, in such a way that pre-mutational injuries induced by radiation and by DES itself became fixed in the genome.
Keywords: Gamma radiation; Drosophila melanogaster; Resistance.
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