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Title: Influence of P element transposition on quantitative genetic characters of Drosophila melanogaster
Author: McMahon, Robert
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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Experiments designed to quantify the effects of P transposable elements mobilised in dysgenic crosses on quantitative phenotypic variation in the fruit fly Drosophila melanogaster are reported. Comparison of previously isogenic IInd chromosomes exposed to P elements in dysgenic (female parent lacking elements ) or non-dysgenic (female parent carrying elements) hybrid flies indicated that there was significantly more variation among the former. Estimates of induced mutational variance VM/VE = 0.06 and 0.37 were obtained for the abdominal and sternopleural bristle scores among the dysgenic chromosomes, which also showed a significant 25% reduction in viability relative to the controls. In a second series of experiments, IInd and IIrd chromosome pairs, isolated from dysgenic F1 flies, were compared to originally isogenic chromosomes which had been isolated using balancer strains lacking P elements. Three independent comparisons of the variation in these groups were made, and a combined estimate of VM/VE = = 0.124 ± 0.03 calculated for the abdominal bristle score. On average, a line was found to contain 3.5 elements, giving an estimated V_M/V_E = 0.035 ± 0.006 for single homozygous inserts. Regression of squared deviations of line means from the population mean gave estimates of the effect of a homozygous inserts of approximately 2% of the environmental variance. One quarter of the dysgenic derived chromosomes were recessive lethal when isolated, 0.1 appeared near lethal, and a significant reduction of 10% viability was found among a sample of the remainder, compared to uncontaminated controls. These effects were found to be correlated with the number of elements in the lines, and estimates of a 3% ± 2.4% drop in viability and 0.06 lethals per insert were made. None of the monitored lines converted to P cytotype during the 12 generations for which they were observed, although several harboured active P elements.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available