The cell cycle is the sequence of events in a cell that culminate in cell division.


When a cell is not in the process of dividing, it is in a phase known as interphase.

During interphase, which is the longest part of the cell cycle, the cell is preparing to divide.

In eukaryotic cells - a eukaryotic cell has a nucleus; cells without nuclei are known as prokaryotic cells - interphase can broken down into three shorter stages:

  1. G1 (Gap 1)
  2. S (Synthesis)
  3. G2 (Gap 2)

Chromosomes are duplicated during the S phase, in preparation for cell division.

During the G1 and G2 phases, cells grow and are metabolically active, but chromosomes are not replicated.

Mitotic phase

After the G2 phase, interphase ends and the cell enters the M (Mitotic) phase.

The M phase consists of two stages:

  1. Mitosis - The nucleus splits to form two new nuclei, each with identical sets of chromosomes.
  2. Cytokinesis - The whole cell divides in half, so two new cells are created.

G0 Phase

If a cell does not receive enough nutrients, it will enter a G0 phase.  This is a stationery phase, in which the cell cycle stops and the cell does not grow or divide.

When nutrients are replenished, the cell cycle will resume.

The G0 phase is an important part of the cell cycle in multicellular organisms.

If all of the cells in a multicellular creature had to grow and reproduce constantly, some types of cells would become too prolific.

Cells in multicellular organisms are usually in the G0 phase.

Once they have reached maturity, human muscle cells and human nerve cells remain in the G0 phase all the time.

The length of the cell cycle, and the proportion of time spent in each phase of the cycle, is different for different kinds of eukaryotic cells.