Fig. 5. Rb-deficient cells undergo complete ectopic mitoses. Sections were labeled with an antibody against the M phase marker phospho- histone H3 (PH3) at E16.5. In contrast to the control, the mutant exhibited widespread mitoses outside the ventricular zone (coronal). Boxed areas (A and B) are magnified (C and D) (n = 4). Bar = 25 µm.