March 2007

Tags: Basics, chromosomes, mitosis

How do we grow?
Mitosis is the ordinary type of cell division that all our body cells (except egg and sperm cells) undergo. Mitosis is important for the body to grow and develop and to repair tissues.
Mitosis starts with one body cell containing 46 chromosomes (23 pairs of chromosomes) that replicates its DNA once and divides once to produce two new cells that each have a complete set of 46 chromosomes. Importantly, the 2 new cells produced are genetically identical to the original cell.
Mitosis is just one phase in a cell’s life cycle. A typical body cell passes through three general phases: interphase, mitosis and cytokinesis.

• Interphase is the time between two consecutive mitoses. In this phase cells carry out their normal jobs (G1 phase), and then at some point replicate their DNA (S phase). Chromosomes would now consist of two sister chromatids. The cells then pass through another brief phase (G2).
• Mitosis is the phase where the nucleus divides. The sister chromatids split to ensure two new cells are produced with identical information to the original cell.
• The process of cytokinesis makes sure that the original cell’s cytoplasm is split evenly amongst the two new cells. In this way two clones of the original cell are produced.

To get a clear picture of this truly wonderful process, take a look at our Mitosis animation