Cells overexpressing GFP-GEF and constitutively activated RasB have a cytokinesis defect. (A) Cytokinesis is normal in wild-type AX2 and gefQ⁻ cells but is defective in GFP-GEF cells. Images were taken using a fluorescent microscope (DMR). Images were acquired with a camera (DC 350 FX). (B) The increase in the number of nuclei in GFP-GEF cells. GFP-GEF cells were grown in suspension, fixed at the indicated times, stained with DAPI, and the nuclei were counted. The data are the mean of three independent determinations ±SD. (C) Cytokinesis defect in cells overexpressing constitutively activated RasB^G12T (GFP-RasB^CA; green). Cells were fixed with methanol and nuclei are visualized with DAPI (blue). Arrowheads indicate multinucleated cells. Images were taken using a fluorescent microscope (DMR). Images were acquired with a camera (DC 350 FX). Bars, 10 μm.