We derived inbred lines from the Raleigh, USA population by 20 generations of full-sib mating. We used the C(2L)RM-P1, b1; C(2R)RM-SKIA, cn1bw1 compound autosome (CA) stock for fitness assays. P-element mutations and co-isogenic control lines were a gift of H. Bellen (Howard Hughes Medical Institute, Baylor College of Medicine). We reared flies on cornmeal-molasses-agar medium at 25 °C, 60–75% relative humidity and a 12-h light-dark cycle unless otherwise specified.