The Cell Cycle

Interphase

As the cell progresses through the cell cycle it goes through two phases- interphase and the mitotic phase. Interphase makes up the majority of the cell’s life cycle, and is divided up into several phases. The first phase, G1, is where the cell grows and makes the organelles and proteins necessary to its proper functioning. Nutrients are stored and enzymes are synthesized, stocking up stores the cell will need throughout its life. At the end of G1 the cell goes through two checkpoints: the Nutrient Checkpoint and the R point. The nutrient checkpoint determines whether or not the cell has stored enough nutrients to continue to the next phase and the R point (Restriction point) is where the cell becomes fully committed to the mitotic pathway- it can no longer enter G0 and halt its growth when it has passed this point.

From G1 the cell enters S-phase. During the S phase the cell is busy making copies of its DNA until it has two full sets- these two copies will be (ideally) evenly divided between the daughter cells when the cell finally undergoes mitosis.

The next phase of the cell cycle is G2- during G2 the cell follows a program that looks a lot like G1. It makes proteins and other building blocks necessary to the cell’s function, as well as continues growth. Once the cell has passed through G2 it enters the mitotic phase and begins its division.