Explain the link between cancer and mitosis. Describe how the chances of cancer developing in the human body may be increased.
Explain the link between cancer and mitosis. Describe how the chances of cancer developing in the human body may be increased.
Cancer is one of the most common diseases in the developed countries, accounting for around one in four deaths. In Britain it caused about 25% of the deaths h in 1991 and is the most common cause of death following cardiovascular disease. There are, in fact, over 200 different forms of cancer, which is why it is not necessarily thought of as a single disease. For example, breast cancer is the most common form in women and lung cancer in men.
Cancers are a result of uncontrolled mitotic cell division, which is the division of one cell to produce two genetically identical daughter cells. The problem is cased by mutations or abnormal activation of the genes which control cell division. We can say that a gene has been mutated if there is a change in one of the bases; for example, one base turns (e.g. adenine) into another base (e.g. thymine). This can lead to uncontrolled cell division. When genes are abnormal (or have been mutated) they are called oncogenes (onkos means tumour), about a hundred of which have been discovered. Cancerous cells will divide uncontrollably and repeatedly forming clones of genetically identical cells. Therefore, thought the mutation may start off in only one cell, it can be passed on to the cells decedents, so the daughter cells will too have the mutated gene. Eventually an irregular mass of relatively undifferentiated cells called a tumour is formed. By the time a tumour is detected it may contain about a thousand, million cells, which show abnormal changes in shape.
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