Worm Breeder's Gazette 7(2): 11
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Wild-type males are more sensitive than wild-type hermaphrodites to inactivation by gamma radiation. This sex-specific difference is observed when eggs are irradiated immediately after collection by the hypochlorite method, but it is more pronounced when irradiation is delayed for 22 hours after egg collection. In the latter case, for example, at a dose of 50 kr, survival of males was only about 5% that of hermaphrodites. In both cases, the difference between the inactivation curves of males and hermaphrodites is in the extent of the shoulders and not in the final inactivation slopes. We considered three explanations for this sex-specific difference. First, the difference could be caused by some artifact in scoring the heavily irradiated males and hermaphrodites. Second, the difference could be due to the different sexual phenotypes per se. And third, the difference could be due to the difference in chromosome composition of the two sexes, that is, hermaphrodites are more radiation resistant because they have two X chromosomes rather than one. These possibilities were tested by examining the gamma radiation sensitivities of animals in which the normal correspondence between X chromosome constitution and sexual phenotype was altered by either a her-1 or tra-1 mutation. A her-1 dpy-21 triple mutant was constructed and assayed for radiation sensitivity. The him- 5 mutation insures the constant generation of XO animals; the dpy-21 mutation allows distinction of XO (non-Dpy) versus XX (Dpy) animals; and her-1 transforms XO animals into hermaphrodites. The inactivation curves for non-Dpy (XO) and Dpy (XX) her-1 hermaphrodites were strikingly similar to the curves obtained for wild-type males and hermaphrodites. respectively. Moreover, XX animals transformed into fertile males by a tra-1 mutation did not show increased radiosensitivity relative to their tra-1/dpy-18 sibs. We conclude that the wild-type sex-specific difference is caused by the difference in X chromosome constitution and that inactivation of XO animals by gamma radiation is predominantly due to X-chromosome damage. No sex- specific difference in inactivation was observed after UV irradiation.