Cell CycleCell Cycle ProteinsCell Cycle CheckpointsG1 PhaseMitosisS PhaseCell DivisionCyclinsG2 PhaseMenstrual CycleApoptosisCyclin-Dependent Kinase Inhibitor p21Cyclin-Dependent Kinase Inhibitor p27Cell ProliferationRetinoblastoma ProteinG2 Phase Cell Cycle CheckpointsG0 PhasePhosphorylationCell Line, TumorCDC2 Protein KinaseTumor Suppressor Protein p53Cell LineG1 Phase Cell Cycle CheckpointsProtein-Serine-Threonine KinasesMolecular Sequence DataCyclin-Dependent Kinase 2