Mitosis is a form of nuclear division in which the nucleus divides to form two nuclei, each containing identical sets of chromosomes.
Function of Mitosis:
In single celled organisms its function is to increase the number of individuals. This is known as asexual reproduction.
In multicellular organisms (example humans) mitosis produces new cells not new individuals.
The function in humans is for :
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growth, and |
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to replace old and damaged cells. |
Normally the rate of mitosis and cell division is carefully controlled by the body. However, if a cell or a group of cells lose their ability to control this 'normal' rate of mitosis and cell division, these cells form a mass of cells called a tumour. These tumours can then be benign or malignant.
Benign is when the cells stop dividing after some time. They are not life threatening and do not invade other tissue cells. Examples of benign tumours are warts, skin 'tags' (small blobs of raised skin).
Malignant tumours are called cancer. They can be life threatening. This is because they invade other tissues and move to other parts of the body.
Cancer is caused when normal genes are altered to form cancer-causing genes called oncogenes. These alterations are brought about by cancer causing agents called carcinogens.
Common carcinogens include:
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Cigarette smoke |
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Ultraviolet radiation (from the sun and sun beds) |
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Asbestos fibres |
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Some viruses |
Most cancers can be cured but early detection and treatment is of paramount importance.
Treatments include:
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Surgery - removing the cells |
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Radiation - burn out cancer cells |
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Chemotherapy - use of chemicals to slow down mitosis. |