Fig. 3. A model depicting the role of the antagonism between RhoA and Rac GTPases in regulating cortical activity during mitosis and cytokinesis. The arrows denote the cortical forces that mediate cell rounding during mitosis and cleavage ingression during cytokinesis. Equilibrium between RhoA (blue) and Rac (yellow) activities generates a `green' rigid cortex and the relative forces necessary for cell rounding during mitosis. The `blue' ring indicates the high RhoA activity at the equatorial cortex required for contractile ring formation and furrow ingression. The rectangles illustrate a view from the top of the actomyosin filaments at the equatorial cortex.