Fig. 6. RNA interference experiments. The upper left panel shows the transcript levels for RP49, as an internal control, and of btd and Sp1. Lanes 1 and 3 show normal levels of btd and Sp1 in control btd-Gal4 larvae. Lane 2 shows decreased btd levels in a btd-Gal4>UAS-btdi larva (compare with lane 1). Lane 4 shows the very low Sp1 transcript levels in btd-Gal4>UAS-Sp1i in comparison with control (lane 3). (A) Wild-type antenna. Antennal segments I, II and III, and the arista (ar) are indicated. (B) Antenna of a fly of genotype btd-Gal4>UAS-btdi UAS-Sp1i. Note the reduction in size of the segments I and II. (C) Legs of a fly of the same genotype. All leg segments are reduced in size and often fuse.