Mitosis and the Cell Cycle

The Cell Cycle

Most cells in the body go through a cell cycle. This cycle is tightly controlled and it has four stages.

  • G1 Phase – Gap Phase 1: Every sub-cellular structure (organelle) within the cell is doubled (except chromosomes).
  • S Phase – Synthesis: The DNA replicates to form two copies of each chromosome. Within the cell, 23 pairs of chromosomes become 46 pairs of chromosomes.
  • G2 Phase – Gap Phase 2: Chromosomes within the cell are checked for errors to ensure that no errors are passed down to daughter cells.
  • M Phase Mitosis: In this stage, the cell divides into two identical daughter cells.

Mitosis is the final stage of the cell cycle.

Calculating the length of stages in the cell cycle

We can use this formula to calculate the length of different stages of the cell cycle:


Mitosis is a type of cell division that produces two identical diploid daughter cells. The daughter cells produced from mitosis are clones of each other, which means their DNA is identical.

They are also genetically identical to the parent cell. This way all your cells have an identical DNA composition.

REMEMBER! There are 23 pairs of chromosomes in each cell of the body

Stages of mitosis

The stages of mitosis are prophase, metaphase, anaphase and telophase.

Interphase – This phase must happen before Mitosis begins. G1, S and G2 stages of the cell cycle occur during interphase. The cell spends most of its life in this phase. Mitosis produces two diploid cells from one diploid cell, so chromosome numbers must double before mitosis occurs. The DNA in chromosomes must duplicate themselves in preparation for mitosis and this occurs here!

1. Prophase – The DNA in chromosomes and their copies condense to become more visible. Also, the membrane around the nucleus disappears.

2. Metaphase – Chromosomes and their copies line up in the middle of the cell.

3. Anaphase – Chromosomes and their copies are pulled to different ends of the cell.

4. Telophase – New membranes form around the chromosomes at each end of the cell. The cell membrane pinches in and eventually divides into two daughter cells, which is called cytokinesis.

Mitosis is continuously occurring throughout our bodies.

Why does Mitosis occur?

Mitosis produces new cells and replaces cells that are old, lost or damaged. For you to stay alive and fully functional, these cells need to be continuously replaced. Mitosis is the reason we can grow, heal wounds, and replace damaged cells.

Mitosis is responsible for:

  • Growth for multicellular organisms
  • Repair of damaged tissues
  • Replacement of cells
  • Asexual reproduction in single-celled organisms e.g. amoeba and a few plants. This is the only way that these cells can reproduce.