Chapter 8: Mitosis - Cell Division and Reproduction

Cell-Cycle Control System
There are three critical points at which the cell
cycle is controlled*:
1. G1 Checkpoint: Prevents cell from entering S
phase and duplicating DNA.
Most important checkpoint.
Amitotic cells (muscle and nerve cells) are frozen here.
2. G2 Checkpoint: Prevents cell from entering
mitosis.
3. M Checkpoint: Prevents cell from entering
cytokinesis.
*Cells must have proper growth factors to get
through each checkpoint.