Fig. 7. Activation of the SCR target gene PB by ectopically expressed disco and Scr. (A) The ectopic expression of Scr, using the prd-Gal4 driver, sometimes results in weak PB activation in some affected segments. The embryo shown was chosen because it was among the most strongly staining for PB accumulation. (B) By contrast, expressing both disco and Scr in embryos caused significantly increased ectopic PB accumulation, easily visible in each affected segment in all expressing embryos. mx, maxillary; lb, labial; t2, second thoracic; a, abdominal segments.