Worm Breeder's Gazette 6(1): 33
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.
The mutation mn158 was originally identified on the basis of its conferring hypersensitivity to UV irradiation. Tentatively assigned the gene name rad-4, it has been backcrossed twice to wild type and was positioned about 11 map units to the left of dpy-11 V. rad-4 mutants exhibit a significant decrease in spontaneous meiotic nondisjunction of the X chromosome: 90 broods reared at 25 C yielded 3 males out of 9,689 total self-progeny (0.03%). This compares with 0. 32% obtained at 25 C for N2 (18/5,542). X nondisjunction in him-1( e879); utants was less than 20% of that obtained for him-1; 3.7% (37/1000) for him-1; 1.7% (462/1,457) for him-1. This reduction is not due to a selection against males per se, since rad-4 does not substantially influence X nondisjunction in him-5(e1467) or him-8( e1489) mutants. Moreover, rad-4 male stocks are easily maintained, once established by heat shock. rad-4 appears to be cold sensitive, with high egg inviability at 15 C. Possible allelism with him-7(e1480) and interactions with other him mutants are under investigation. While there are numerous examples of mutations which confer elevated levels of meiotic nondisjunction in C. elegans (Hodgkin et al., 1979, Genetics 91, 67), as well as in many other organisms (Baker et al., 1976, Ann. Rev. Genet. 10, 53), we are unaware of any other mutations that act to reduce nondisjunction.