(C) According to the classical model of cell cycle control, D-type cyclins and CDK4 or CDK6 regulate events in early G1 phase (not shown), cyclin E-CDK2 triggers S phase, cyclin A-CDK2 and cyclin ...

To their surprise, the researchers found that the dry mass of cells actually decreases when they enter the cell division cycle. This mass is regained later on, before division is complete.