Worm Breeder's Gazette 9(3): 16
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 have analyzed the gene structures of 31 spontaneous unc-22 mutations obtained in various of our mutator strains. The mutator strains are in widespread use for Tc1-tagging of genes, and it is important to know the types of mutations that occur in these strains. We have done total genomic Southern blots of unc-22 mutants using 25 kb. of unc-22 as probe. We find that 28 of 31 mutator-induced mutations contain insertions within unc-22. Most of these insertions ( 21) are 1.6 kb and are Cut with enzymes expected for Tc1. Seven mutants, however, contain insertions that are not 1.6 kb. Five inserts are larger than Tc1, approximately 2-3 kb in length. This group is heterogeneous in size and in restriction enzyme cleavage sites. Two inserts are smaller than Tc1, approximately 0.7-1.0 kb in length. We have never observed such insertions when analyzing mutations that occur in Bergerac. In Bergerac and in backcrossed derivatives of Bergerac, we have identified a total of 28 insertion-containing mutations affecting either unc-22 or unc-54. All 28 insertions are 1.6 kb., and based upon Southern blots or DNA sequencing all of them appear to be Tc1. The seven novel insertions are candidates for new transposable elements or for Tc I -related elements of abnormal size. We believe that these mutations are transposon insertions (as opposed to gene rearrangements) because four of them (the only four that have been tested) revert to wild type at high frequency. Revertants do not contain insertions. We are currently cloning these seven alleles to confirm that they are insertions and to analyze the nature of the inserted DNA. We would like to know if these elements are related to Tc1. For example, the smaller insertions could represent deleted derivatives of Tc 1, and the larger insertions could represent more complex Tc1 elements. If the inserts are unrelated to Tc1, then other families of transposable elements are influenced by the mutator mutations.