Worm Breeder's Gazette 12(5): 89 (February 1, 1993)

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.

Mapping of the rec-1 Mutation

Monique-Claire Zetka, AM M. Rose

Dept. of Medical Genetics, 6174 University Blvd., University of British Columbia, Vancouva, B.C., V6 T lZ3 .

The rec-1 ( s180 )mutation was first described by Rose and Bailllie (1979a) as a general recombination enhancer which increased the frequency of meiotic recombination on all linkage groups approximately three-fold. rec-1 wasshown to behave in a recessive manner, suggesting the mutation lies in a gene. To facilitate the study of this interesting mutation, it was necessary to obtain a genetic map position. Since rec-1 behaved recessively, it could be mapped using duplications and deficiencies covering large regions of the genome. sDp1 (I;Ä),a large duplication of the right end of LG I, and sDp2 (I;Ä),a duplication of the left end of LG I were tested for suppression of the Rec-1 phenotype. If the rec-1 locus was included in sDp2 ,a wildtype allele of the gene would be present on the duplication and one would expect the rec-1 phenotype to be suppressed. Recombination was measured in individuals of the genotype sDp2 / dpy-5 unc-13 rec-1 /+ + rec-1 and sDp2 / dpy5 unc-13 rec-1 /+ + + . The relative number of recombinants recovered in sDp2 -bearingindividuals homozygous for rec-1 was three times that recovered for sDp2 -bearingindividuals heterozygous for rec-1 ,indicating that sDp2 did include the rec-1 locus. Similarly, recombination was measured in sDp1 / dpy-5 dpy-14 rec-1 /+ + rec-1 hermaphrodites and sDp1 / dpy-5 dpy-14 rec-1 /+ + + controls. The frequency of recombination in dpy-5 dpy-14 /+ + heterozygotes is 0.013 whereas in dpy-5 dpy-14 rec-1 /+ + rec-1 individuals, this frequency is enhanced to 0.055. In sDp1 -bearingindividuals heterozygous for rec-1 ,the frequency of recombination in this interval was 0.016. In sDp1 -bearingindividuals homozygous for rec-1 ,the frequency of recombination in this interval was 0.018, indicating that sDp1 carried a wild-type allele of rec-1 .To obtain a better map position, deficiencies of the right end of the chromosome were tested for failure to complement rec-1 .Recombination was measured in individuals of the genotype eDÄX/ rec-1 ; dpy-11 unc42 /+ + . The deficiencies eDÄ4, eDÄ9, eDÄ1O and eDÄ13 all complement the ribosomal deficiency eDÄ24, and all complemented rec-1 .In eDÄ24/ rec-1 ; dpy-11 unc-42 /+ + individuals however, the frequency of recombination was 0.030, compared to 0.056 observed in eDÄ24/ +; dpy-11 unc42 /+ + controls. This result has placed rec-1 locus within the boundaries of eDf24 .This region is spanned by six overlapping cosmids between unc-54 and rrn-1 .Three of these have been injected into a Rec-1 hermaphrodite to generate a transformed line (J. McDowall, unpublished results). This line has been tested for suppression of the rec-1 phenotype by assaying the frequency of recombination in the dpy-11 unc-42 interval. The frequency of crossing over observed in this line was characteristic of Rec-1 ,indicating the cosmids did not rescue the mutant phenotype. An effort is now under way to generate another transformed line with the remaining three cosmids and to map the breakpoints of eDÄ24 on the physical map using PCR with the intention of cloning this interesting and elusive gene.