Fig. 3. The increase in Dup levels in response to replication stress is not sensitive to ATM/ATR-checkpoint-kinase activity. Dup labeling in a single third-instar brain lobe from HU-fed wild-type (A), HU-fed mei-41^29D mutant (B) and HU-plus caffeine-fed wild-type (C) larvae. (D) High-power image of cells from an HU-treated mei-41^29D brain labeled for Dup (red) and PH3 (green). Some mei-41^29D cells proceeded into mitosis in the presence of HU and had chromosomes that were highly aberrant in morphology. Arrow indicates a neuroblast stem cell (NB). Scale bars, 10 µm.