Magnesium and manganese ions as protection against X-ray induced dominant lethal mutations in Drosophila Melanogaster
King, Richard J.
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The purpose of this study was to test whether magnesium or manganese ions could confer protection against the effects of irradiation upon chromosomes and to test for differences between hatchabilities of eggs laid within the first two days after mating and eggs laid during the third day after mating. Male Drosophila melanogaster flies from an inbred stock were injected with magnesium or manganese (II) chloride at a concentration of .01453 M. and then irradiated with 1600r of X-rays. Using three day old virgin females of the same strain, the males were then mated daily for twelve days in a ratio of one male:two females. X-ray induced dominant lethality was assayed using the percentage of unhatched eggs resulting from these matings. No difference was observed between the hatchabilities of the two types of egg-laying, so these data were combined for analysis. The dominant lethality of the unirradiated groups approximated five per cent while that of the irradiated groups varied from ten to ninety- four per cent. The magnesium chloride—-X-ray treatment resulted in the highest dominant lethality obtained for two successive brood days, Days 8 and 9, thus indicating that the chromosomes had been sensitized to irradiation. The cells sampled on these brood days were in early meiosis at the time of irradiation. This study showed that treatment with magnesium chloride alone protects against spontaneous dominant lethality as compared to an uninjected control. As compared to an uninjected irradiated control, treatment with magnesium chloride protects spermatids and spermatogonia against X-ray induced dominant lethality although it enhances dominant lethality in spermatocytes, and manganese (II) chloride protects late spermatocytes. Comparing whole groups, both magnesium and manganese (II) chloride protect against X-ray induced dominant lethality as compared to an uninjected irradiated control. Neither salt, however, was able to reduce the dominant lethality to the level observed for unirradiated flies.