The Genetic Analysis of Negative Geotaxis Behavior in Drosophila Melanogaster

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Title: The Genetic Analysis of Negative Geotaxis Behavior in Drosophila Melanogaster
Author: Shuford, David Tice Jr.
Advisors: Dr. Robert Anholt, Committee Member
Dr. Pat Estes, Committee Member
Dr. Trudy Mackay, Committee Chair
Abstract: Behaviors are complex traits, which exhibit continuous phenotypic variation in natural populations. The continuous variation is attributable to the segregation of multiple interacting loci with individually small effects on behavior, which are sensitive to the environment. In Drosophila, loci with small, environmentally sensitive effects on behavior can be identified by screening collections of P-element insertions that have been generated in a co-isogenic background. Here, we have used this approach to identify novel candidate genes affecting geotaxis. Drosophila melanogaster are negatively geotactic, i.e., flies move opposite the Earth's gravitational vector when disturbed. We developed a rapid assay to quantify this geotactic behavior. Individual flies are placed in a 15cm tube, and lightly tapped to the bottom. The vertical distance traveled in 10s is the measure of behavior. Using this assay, we quantified the behavior of 475 co-isogenic P-element insertion lines, generated in co-isogenic Canton-S backgrounds as part of the Berkeley Drosophila Gene Disruption Project. The most extreme scoring lines were also assayed for locomotor activity to control for pleiotropic effects associated with this quantitative trait. We found 24 lines with increased, and 15 lines with decreased geotaxis. Four lines had sex-specific effects on geotactic behavior. Seventeen of the mutations are in known genes, many of which affect neurogenesis (e.g. Mushroom-body expressed and neuralized). The remaining are insertions in predicted genes of unknown function. We tested a subset of lines in the classic geotaxis maze. Of the ten lines chosen to be tested, eight lines showed a significant difference from the parental line, and of these, six lines showed a phenotype that corroborated our observations in the climbing assay. Thus, our approach identified new candidate genes that contribute to geotaxis in Drosophila melanogaster.
Date: 2005-03-09
Degree: MS
Discipline: Genetics

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