Worm Breeder's Gazette 8(3): 91
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 studying the unc-22 f linkage group IV . Our experiments make use of R. Horvitz's balancer nT1. In one experiment devised to study the effect of heat shock mutagenesis in C. elegans , we noticed that when Bergerac (BO) hermaphrodites were mated to Bristol (N2) males, a high rate of mutation was detected both in our control and in our experimental. unc-22 BO hermaphrodites (EMS induced by Teresa Rogalski) were mated to unc-22 1 N2 males. Single wild-type F1's were set and their progeny analyzed for the absence of Unc-22 individuals. Of 537 chromosomes screened, 24 lethal bearing chromosomes were recovered (4-5%). This is an increase of approximately 50 fold over the spontaneous rate of lethal induction in the Bristol strain (Rosenbluth et. al., Mutation Research 110:39-48). Several of these mutations have been mapped relative to unc-22 . One maps 8.5 map units from unc-22 , another maps 4 map units away. Of interest are three independently derived mutations which fail to complement one another and let-52 and appear tightly linked to unc-22 . These mutations may either be point mutations of let-52 or may be chromosomal rearrangements in this region. We are able to detect lethal bearing chromosomes in the progeny of the F1 suggesting that the mutations are fixed in the F1. Therefore, two possibilities exist as to the nature of these mutations. The unc-22 BO strain may have an unusually high spontaneous mutation rate. Alternatively, the high mutation rate may be due to a hybrid dysgenesis-like phenomenon, occurring sometime after fertilization and prior to the development of the germline of the F1. If the unc-22 BO strain had an endogenous high spontaneous mutation rate, one would expect a large number of clustered mutational events. We have evidence of one such event. We are in the process of establishing a N2/BO let-52 strain which has been repetitively backcrossed to Bergerac. Examination of this strain may allow us to detect reversion. Also of interest is the distribution of these lethals. EMS induced lethals seem to be primarily to the left of unc-22 . There is only one EMS induced allele of let-52 , while there are three N2/BO interstrain cross induced alleles. The molecular basis of these mutations is being investigated. If these mutations are due to transposable element insertions, either Tc1 or some other element, it will be possible to isolate insertional mutations in genes of interest. These molecularly marked strains will be invaluable for the cloning and molecular identification of specific genes.