Worm Breeder's Gazette 8(3): 9
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.
We are currently investigating the genetic organization of the region of linkage group I covered by sDp2. A novel 'lethal-capture' system which uses a free duplication of the left third of LG I, sDp2, is being used to isolate lethals and steriles in this region. 'Wildtype' hermaphrodites of the genotype sDp2/dpy-5 unc-15/dpy-5 e diploid individuals that are Dpys and two types of Dpy-Uncs, and duplication-carrying individuals that are 'wild- types' and two types of Uncs. 'Wild-type' hermaphrodites were treated with 0.01M EMS or 1500R gamma radiation. Five to ten F1 'Wts' from each P0 were placed individually on small plates. These were screened for the absence of one of the Dpy-Uncs in the F2 generation. Adult steriles were isolated by screening for Dpy-Uncs without eggs. Since both of the chromosomes are marked it is possible to isolate lethals induced on either chromosome. However we preferred to screen for lack of Dpy-Unc-13's and work with Unc-13's. Lethals were maintained as Unc-13s with the genotype sDp2/let dpy-5 t unc-13. Crossing-over between sDp2 and the normal homologue does not occur (Rose et al, 1984 MGG 195:52-56) so that the lethals are maintained in a homozygous state recovered by the wild- type allele on the duplication. Thus, for the duplicated region the lethals are completely 'balanced'. The extent of the duplication strictly defines the region in which lethals can be isolated. In addition, the fact that the lethals are maintained homozygous makes it easy to generate heterozygotes for mapping and complementation tests. The screen is relatively simple and efficient. The induction frequencies are comparable to those predicted by the eT1 data of Rosenbluth et al (1983 Mutation Res. 110:39-48). eT1 covers approximately three times as many map units as sDp2.[See Figure 1] We are recombination mapping the lethal and adult sterile mutations. Lethal homozygotes carrying sDp2 are crossed to N2 males. Wild type outcross hermaphrodites which do not carry sDp2 (the presence of the duplication causes a characteristic mildly Unc phenotype and slower development) are allowed to self, and their progeny are scored. Recombinant Dpy's are found if the lethal mutation is to the right of dpy-5, and recombinant Dpy-Uncs are found if it is to the left. All of the lethals are being complementation tested to sDf4 and hDf1. All those which fail to complement sDf4 are being subjected to inter se complementation tests. One complementation group has been identified which includes h46 (an EMS-induced mutation) and h54 (a gamma-induced mutation). More mutations are being isolated so that we may attempt to define the organization of essential genes in this region. [See Figure 2]
