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.

The Gene Structures of Mutator-Induced Mutations

J. Collins, B. Forbes and P. Anderson

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