Cells that are growing and dividing go through a repeating series of events called the cell division cycle (or cell cycle). During the first phase (G1), the cell grows and prepares for DNA replication, which occurs in the subsequent S phase. Further growth takes place in the G2 phase, and finally mitosis occurs in the M phase.
• G1, S, and G2 are collectively called interphase.
• G1 stands for gap 1, or presynthesis; S for synthesis; G2 for gap 2, or postsynthesis.