Fig. 1. Dl and Ser act redundantly during lateral inhibition. Third instar nota are stained for Senseless (red), to visualize SOPs. Proximal is upwards, anterior is towards the left. Scale bar: 40 µm. (A) Notch mutant cells marked by absence of GFP. (B-F) Mutant cells marked by presence of GFP. (A'-F') Red/Sens channels of A-F, respectively; mutant areas are indicated by arrows. (A) N or (B) Dl Ser clones display a large number of clustered ectopic SOPs. This phenotype probably represents the complete loss of lateral inhibition. By contrast, (C) Dl mutant clones show only a few ectopic SOPs and (D) Ser mutant clones appear wild type. (E) Dl mutant clones simultaneously expressing UAS-fng display a more severe phenotype than Dl (C). (F) Dl Ser mutant clones expressing UAS-Ser appear wild type.