To perform a geotaxis assay, first attach a clean, empty bottle cap to each end of the choice chamber and turn the fly vial upside down onto its lid.
Open the tape flap in the center of the choice chamber.
Insert the funnel into the hole and tap all of the flies into the chamber. HYPOTHESES: The alternate hypothesis is that more flies will be moving against gravity, or up, regardless of the orientation of the choice chamber. Alternatively, if the flies are positively geotactic, then more flies will move down, or with gravity. The null hypothesis is that the flies will have no preference with regard to gravity and will move randomly within the chamber.
Once the Drosophila are in the chamber, close the tape flap, rotate the chamber so that it stands vertically with side A on the bottom, and start the timer.
Immediately, count the number of Drosophila that are moving up and the number that are moving down. Record these data for time point 0 in the table.
After 30 seconds, rotate the chamber so that side B is on the bottom and count the number of Drosophila that are moving up or down. Record these data for time point 30 in the table.
After 60 seconds, rotate the chamber so that side A is on the bottom again and record the number of moving flies for time point 60.
Click Here to download Table 1
Hold the chamber over the fly vial and carefully open the cap to return all of the Drosophila back to their empty vial.