Developmental Biology 细胞增殖受内外因素的控制 Fig. 14.2 The eukaryotic cell cycle After mitosis(M), the daughter cells can either enter a resting phase(Go), in which they effectively withdraw from the cell Resting cycle, or proceed through Gt to the phase of DNA synthesis(S). This is followed by DIVISIOn G2, and then by mitosis. Cell growth occurs throughout G1, S, and G2. The decision to enter Go or to proceed through G1 IGrowth may be controlled by both intracellular factors status and extracellular signals, such as growth factors. Cells such as neurons cephas and skeletal muscle cells, which do not divide after differentiation are permanently in Go During cleavage of fertilized eg there are virtually no G-phaseDevelopmental Biology 细胞增殖受内外因素的控制 During cleavage of fertilized eggs, there are virtually no G-phase