Worm Breeder's Gazette 9(3): 31
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.
As part of our ongoing genetic analysis into the organization of essential genes on LGIV (right) and LGV (left), we have conducted a screen for Tc1-induced lethal mutations in these regions. A strain was constructed with the mutator activity on LGI (derived from RW7037, Moerman and Waterston, 1984, Genetics, 108:859-877) and the balancer, nT1 (Ferguson and Horvitz, 1985, Genetics, 110:170-72), which suppresses recombination on LGIV from almost unc-17 to dpy-4 and on LGV from unc-60 to at least sma-1 [approximately 40 m.u. overall). The genotype of the strain used for our screen was mut-4/mut-4 (I?;unc- 22/nT1(IV);unc-46/nT1(V)]. We screened 3503 F1 'chromosomes' and 35 lethal mutations were recovered: a rate of 1%. In order to reduce the likelihood of reversion or further Tc1-induced mutations, each strain was outcrossed and the 'mutator' chromosome was segregated out. This was done by using a dpy-5 marked chromosome [see Mori et al., WBG 9(1), p. 25]. So far, 7 lethals have mapped to LGIV and 23 to LGV. Comparison with EMS mutagenesis data [4.4% lethals on LGIV, 3.4% lethals on LGV; see WBG 9(2), p. 82] indicates that there is probably a mutational hotspot for Tc1 on LGV. The deficiency mapping and inter se complementation tests of these lethals, now in progress, will indicate if this is the case. Tc1-tagged essential genes will be extremely useful for characterization and positioning of cloned sequences with respect to the genetic maps of LGIV(right) and LGV(left).