Interphase

The mitotic phase is a relatively short period of the cell cycle. It alternates with the much longer interphase, where the cell prepares itself for cell division. Interphase is divided into three phases: G1 (first gap), S (synthesis), and G2 (second gap). During all three phases, the cell grows by producing proteins and cytoplasmic organelles. However, chromosomes are replicated only during the S phase. Thus, a cell grows (G1), continues to grow as it duplicates its chromosomes (S), grows more and prepares for mitosis (G2), and finally it divides (M) before restarting the cycle.[9] All these phases in the cell cycle are highly regulated, mainly via proteins. The phases follow one another in strict order and there are "checkpoints" that give the cell the cues to proceed from one phase to another. There is also a fourth section in Interphase where the cell has the option to enter G0. Cells continue on through this cell cycle until they become too crowded; at that point they will exit the cell cycle and enter G0. This reaction is called contact inhibition or density-dependent inhibition. Altogether interphase takes up roughly 90% of a cell's lifespan.