Genetics - Theses
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ItemInvestigations of Drosophila melanogaster as a model for insecticide resistance studies(University of Melbourne, 1991)Standard techniques were defined for using Drosophila melanogaster as a model organism for insecticide-resistance studies. The dosage mortality curves for sensitve (wild-type (WT)) strains (CS and attached-X) challenged with dieldrin, diazinon and cyromazine were defined to choose a concentration to screen for monogenically resistant survivors. Ethylmethanosulphonate mutagenesis was used to create diversity within the sensitive populations prior to screening. From a screen of 600,000 embryos, and the rescreening of 160 survivors, two stabley cyromazine resistant strains were isolated. By standard mapping techniques the resistance in these two strains was found to be conferred by different genes (or gene complexes), designated Cyr-1 and Cyr-2. These mapped respectively within 1 m.u. of ri on chromosome III, and in the region of vg on chromosome II. The dosage mortality for various combinations of the resistance alleles showed that Cyr-1 confers 3xWT tolerance when heterozygous and homozygous, while Cyr-2 confers 2xWT when heterozygous and 4xWT when homozygous. Fitness tests on the resistance alleles showed that Cyr-1 causes a significant decrease in developmental time and survival compared with CS. Neither of the resistance alleles, however, appear to affect developmental homeostasis since the asymmetry values of resistant strains are similar to that of WT. It is argued on the basis of these results, with some modification to the techniques, that Drosophila melanogaster can be a useful model for studying the inheritance of resistance.