A P element insertion in the dmyc locus is a reporter for dmyc activity. (A) A diagram indicating the exons (green rectangles) and introns (thick blue line) of the dmyc gene on the X chromosome. A pGT1 insertion in the second intron (dmycBG 02383, top) inserts the Gal4 (blue rectangle) and mini-white (red rectangle) reporters. A second insertion upstream of the dmyc transcription site is also shown (dmycBG 00605, bottom) (B) Gal4 and mini-white reporters exhibit dmyc autorepression. RT-PCR amplification products are shown from embryos with dmycBG 02383having Gal4 or Gal4; UAS-dmyc transgenes, and therefore wild type for Myc (wt) or producing ectopic Myc (Myc++), respectively. The numbers under each band indicate the relative band intensities between pairs as indicated by phosphorimaging. (C) Scheme for genetic screen for modifiers of dmyc activity. Females homozygous for dmycBG 02383on the X Chromosome were crossed to males of the Second and Third Chromosome deficiency "kits" (Bloomington). Fly heads are depicted in profile, cartooning the changes in eye color expected when a fly has both dmycBG 02383and either a mutation in a dmyc activator (upper right) or a mutation in a dmyc repressor (lower right).