Cell-cvcle Continuously cycling 细胞周期 (e.g, epidermis) labile cells A DNA synthesis G1 Cyclins-CDKS C、D、E 2 M Mitosis B Quiescent stable cells (e. g, cardiac myocyte) (e. g, hepatocytes) (e. g, neuron) Nondividing permanent cellsCell-cycle 细胞周期 Cyclins-CDKs A B C、D、E