S phase

Cell Cycle Regulation Cell cycle control systems The frequency of cell division varies with the type of cell Caused by the difference in regulation at the molecular level The stages of the cell cycle are regulated by a distinct cell cycle control system (similar to a clock) The cell cycle control system is regulated by both internal and external controls The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received Cell cycle control systems: interphase and mitosis Interphase Makes up about 90% of the cell cycle: can be divided into subphases: G1 phase (?first gap?) S phase (?synthesis?) G2 phase (?second gap?) The cell grows during all three phases Chromosomes are only duplicated during the S phase