Keene State College
Mentor: Dr. W. Kelley Thomas, Department of Biochemistry
Variation in Geotaxic Behavior among Wild Populations of Drosophila
For many years biologists have been trying to discover how genes affect behavior. In the early 1960's extensive laboratory research was conducted to explore the genetic basis of differences in geotactic behavior, in fruit flies (Erlenmeyer- Kimling 1961, 1962; Hirsh 1961, 1962; Ricker 1985). The fruit fly (Drosophila) exhibits crawling behavior in relation to gravity, called geotaxis. Negative geotaxis is crawling away from gravity; positive geotaxis is crawling towards gravity. The two common techniques for testing geotaxis. behavior are the maze technique and the vial technique. The maze technique allows flies to choose an upward path or a downward path. In the vial technique, flies are timed to determine how fast they move up to a designated point on a vial. By selectively breeding aboratory Drosophila melangaster for either positive or negative geotaxis, scientists have been able to create Drosophila lines that are either strongly negative or strongly positive in the geotaxic behavior. Using modern genomic techniques, Toma et al. were able to identify 250 genes that show differences in gene expression between positive and negative geotaxic flies. They focused on a handful of these genes and identified three (pdf, pen, and cry) that can be responsible for differences in geotaxic behavior (Toma et. al.); it remains to be demonstrated that different Drosophila species have different geotaxic behaviors and if these same genes are responsible for natural variation in geotaxic behavior. This study will investigate whether different species of Drosophila exhibit variation in geotaxic behavior. Furthermore, any flies that are bred in this project can be used at a later date to determine if the same genes affecting geotaxis in laboratory selected populations also affect geotaxis in wild populations, of different Drosophila species.