In the cell cycle, there are three main checkpoints. The first checkpoint is at G1/S, where the cell checks for DNA damage and decides whether or not to continue replicating its DNA. The second checkpoint is at G2/M, where the cell again checks for DNA damage and decides whether or not to enter mitosis. The third and final checkpoint is at metaphase/anaphase, where the cell ensures that all of its chromosomes are properly aligned in order to divide evenly into two new cells.