The meiotic pattern and chromatin structure in Caenorhabditis elegans

In the nematode Caenorhabditis elegans, local variations in frequencies of crossing over have been observed along chromosomes. These variations give rise to a genetic map that differs from the physical map, with a recombinationally suppressed cluster of genes located in the centre of the autosomes and flanked by highly recombinogenic arms. This distribution of crossover events is known as the meiotic pattern. The pattern is modified in a mutant, rec-1. Mutational alteration of the meiotic pattern allows for investigation of the mechanisms governing the generation of the meiotic pattern. In other species, recombination hotspots have been linked to chromatin modifications. In this thesis, I have investigated whether or not chromatin modifiers are required to maintain the unique meiotic pattern found in C. elegans. Mutations in two chromatin modifiers, him-17 and lin-35, were analyzed and found to eliminate the meiotic pattern, producing an increase in the frequency of crossing over within a recombinationally suppressed region, and a decrease in the frequency of crossing over within a highly recombinogenic region. This is the first demonstration that meiotic patterning in C. elegans is established by chromatin structure.Medicine, Faculty ofMedical Genetics, Department ofGraduat