Characterization of the recombination enhancer, rec-1, in Caenorhabditis elegans

The hyper-rec mutation rec-1, in Caenorhabditis elegans, has previously been shown to increase intergenic recombination frequency by a factor of three (Rose and Baillie, 1979a). The further characterization of the effect of rec-1 on recombination and other meiotic processes has been the focus of this thesis. The effect of rec-1 on intragenic recombination, gene conversion, fecundity, competitive ability, nondisjunction and mutation rate were examined. The rec-1 mutation produced a two to three-fold increase in intragenic recombination and gene conversion. Pleiotropic effects are typical of recombination mutants, however, only the rate of X-chromosome nondisjunction and/or chromosome loss was affected by rec-1, exhibiting a two-fold increase relative to the N2 (wild-type) strain. In addition to the above, a strain was constructed to determine if the rec-1 mutation was an amber, nonsense mutation (ie. a premature stop codon, preventing translation). The results showed that the expression of the Rec-1 phenotype was not affected by a tRNA amber suppressor (ie. sup-7). This indicated that rec-1 is not an amber mutation. The affect of rec-1 as a recombination enhancer on the mobility of the transposable element, Tc1, was also examined. Electrophoretic banding patterns produced by DNA restriction fragments probed with Tc1 were compared for the N2 and Rec-1 strains. An altered banding pattern was found, suggesting that rec-1 activates Tc1 mobility. However, predicted differences between two Rec-1 DNA samples (one prepared two years after the other) were not found. Several alternative explanations are considered. High recombination mutations reported in the literature are reviewed and several hypotheses consistent with the above results are considered as possible explanations of the rec-1 enhancer.Medicine, Faculty ofMedical Genetics, Department ofGraduat