| Summary: | The discovery of extreme mutability around the g. locus of Drosophila melanogaster in a certain lab strain, S6-1, led to an investigation of the nature of this phenomenon and any possible relationship it had with the well described P-M hybrid dysgenesis mutator system. Southern gel analysis showed the S6-1 strain to contain P element homology and dysgenic crosses involving this P-strain showed mutability in the germline of the F₁. An unexpected finding was the requirement for the presence of the S6-1 X-chromosome in F₁ dysgenic males in order to produce the germline mutability. In situ hybridization to polytene chromosomes showed the S6-1 strain to have a number of P sites, the majority of which were on the X-chromosome (app. 20/33). These results indicated that the only complete P element or elements were confined to the X-chromosome. The presence of an unexpected third class of orange-eyed males in the F₂ progeny of the cross: S6-1 males x g² females led to the isolation of an enhancer of garnet locus, (e(g), located in the distal region of the S6-1 X-chromosome. This study included an investigation into the nature of the interaction between the e(g) locus and the g; locus and other autosomal loci. The enhancer was found to be specific to the g. locus, and, more specifically, to certain spontaneous alleles located to one end of the fine structure g. locus map. A description is given of the isolation and preparation of a P-induced garnet mutation for molecular analysis. === Medicine, Faculty of === Medical Genetics, Department of === Graduate
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