AET AND RADIATION-INDUCED CROSSING-OVER IN MALE DROSOPHILA MELANOGASTER

¹ Department of Biological Sciences, Northern Illinois University, De Kalb, Illinois 60115

1. Drosophila melanogaster males heterozygous for ru h th st cu sr e⁸ ca were injected with AET and irradiated with 2000 r and backcrossed to "rucuca." The number of induced crossovers with two or more mutants (r₂) was significantly decreased in the 9-12-day broods of males treated with AET as compared to controls.

2. The hypothesis that AET interfered with a recovery process probably by an induced anoxia was tested by N₂-treatment after the x-ray-treatments. The N₂ post-treatments had no effect on AET-treated and irradiated males with respect to crossovers; however, the young spermatogonia represented by brood day 12-15 of the control males were induced by the N₂ treatment to produce less crossovers.

3. Since the AET effect is eliminated by N₂ post-treatment, an anoxia production by AET can be a possible mechanism for reduction of crossovers. Nitrogen post-treatment tends to reduce the number of radiation-induced crossovers. AET did not affect the young spermatogonia.

4. The induced breakage occurred primarily between regions st and cu and thus in or about the centromeric region. AET has no influence on the region of the breakage.

5. Crossovers were found to be more frequent in the 9-12-day brood than in the 12-15-day brood.