Fig. 7. Mutations in bubR1¹ do not affect cyclin B accumulation during G2. (A) bubr1¹ mutant neuroblasts were treated with colchicine as previously described, fixed and stained for DNA (white) and cyclin B (green). The results show that unlike bub3¹, bubR1¹ mutant cells do not compromise accumulation of cyclin B during G2. Nevertheless, as expected, cyclin B levels during mitosis decrease significantly because of loss of spindle checkpoint activity. (B) Quantification of cyclin B levels at different cell cycle stages in Oregon R (wild-type strain) and bubR1¹, was performed as described for bub3¹ (see also supplementary material Table S7). **P<0.005; ***P<0.0005 when compared to intensity in the relevant control cells. Bar, 5 µm.