Cancer - or to inactivate both alleles of a gene which...

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Cancer The aim of this small section is to introduce the idea of cancer as a genetic disease. Although probably a relatively small proportion of all cases of cancer are caused by the inheritance of faulty genes, all cases of cancer are caused by mutation of one (more often several) genes. In addition, for all types of cancer there exist a small and instructive proportion of cases in which the mutation was inherited. Loss of cell cycle control Cancer is caused by the loss of control of cell division. Many cells need to divide for tissue growth or maintenance but this ability must be strictly regulated. When the regulation breaks down and a cell is able to divide unchecked then cancer is the result. The cause of the breakdown is mutation either to cause a gene whose normal function is to stimulate a cell to divide to be over expressed or inappropriately expressed
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Unformatted text preview: or to inactivate both alleles of a gene which functions to prevent cell division. The former class of genes are known as oncogenes and the latter as tumour suppressor genes. Oncogenes Most examples of oncogenes were discovered by molecular virologists working in the 1970s and 80s. They were studying RNA viruses which had the property of transforming cells which they infected from a normal to a cancerous state. The viruses had aquired copies of host genes (protooncogenes) which had mutated (into oncogenes). The normal roles of the genes were varied. Some were growth factors involved in the normal stimulation of cells to divide. Some were growth factor receptor proteins which would now stimulate their targets even without binding external growth factors. Some were themselves transcription factors, directly stimulating other genes....
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