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How inherited genes cause cancer

This page is about how genes cause cancer. There is information about


How genes can cause cancer

Cancers develop from a single cell or a small group of cells. A fault occurs in one or more of the genes in the cells. Usually a cell must have 6 or more gene faults before it becomes cancerous. Scientists call gene faults ‘mutations’. A gene mutation can make a cell stop working properly. It may become cancerous and divide and grow uncontrollably. These gene changes can happen either by developing faults during your lifetime or they can be inherited from a parent. This section is about inherited cancer genes

Most cancers are caused by gene faults that develop during our lifetime. There may be a random mistake when a cell is dividing. Or the cell’s DNA may be damaged by a carcinogen. A carcinogen is something that increases the likelihood of a cancer developing – for example, cigarette smoke.


Inheriting a faulty gene

Some people have an increased risk of particular types of cancer because they already have a gene fault when they are born. They won’t necessarily develop cancer. But they are one step further along the road to developing cancer than people without that gene fault. They are also more likely to develop cancer at a younger age.

We inherit genes from both our parents. If one of your parents has a gene fault you have a 1 in 2 chance (50%) of inheriting it. The more distant your relative with a gene fault is, the lower your chance of inheriting it.


Gene faults don’t always cause cancer

Generally, a cell must gather about 6 specific genetic faults before it becomes cancerous. So being born with one gene fault doesn’t mean that you will definitely get cancer. But you are at a higher risk than someone without that gene fault. Doctors call this having a genetic predisposition to cancer.

Different gene faults increase the risk of different types of cancer. Some faults increase the risk by a small amount and some increase the risk much more. 

If you have a known gene fault, your doctor may suggest that you need regular monitoring for particular cancers or they may suggest treatment to try to reduce the risk of developing cancer.


Faulty genes and other factors

Some inherited cancer genes are more likely to cause cancer than others. It depends on how big a part the gene plays in the development of that cancer. As well as a gene fault, many other factors need to be in place for a cancer to develop. We need more research to find out what these other factors are for each type of cancer. 

We need to find out more about how genes work together to cause cancer so we can reduce the risk of developing it. 

If you have a faulty gene your doctor may be able to give you an idea of how much your risk is increased compared to the general population.

You can find out about other cancer risk factors in the causes and prevention section.

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Updated: 27 March 2015