Comparison of activity and hsp -GFP expression data from different flies. The data for tracking of several different flies over a period of 48 hours is overlaid to allow comparison of fly-to-fly variability in activity (upper panel; distance moved per hour) and GFP intensity (lower panel; average pixel intensity per hour). Black/white bars indicate the light/dark cycle the flies were cultured under prior to the beginning of the experiment. Different colors indicate different individual flies, some of slightly different ages. (A) hsp70-GFP transgenic flies, strain 2MI4. Green, 32 days; Blue, 40 days; Black, 40 days; Red 48 days. The 48-day old fly (Red) dies in the course of the experiment. (B) hsp22-GFP transgenic flies, strain 1MI1. Green, 32 days; Blue, 40 days; Black 40 days; Red, 48 days. The 48-day old fly (Red) dies in the course of the experiment.