Genetics of cancer

DNA is the material we inherit from our parents and makes us who we are. Genes are small sections of our DNA and it is the genes that carry the ‘codes´ (instructions) for telling our cells what they need to do in order for the body to grow and work properly. Cancer can develop when faults occur in our genes so that our cells no longer understand how to behave and they start dividing in an uncontrolled way.

What is the relationship between genes and cancer?

Cancer can develop when a normal cell starts behaving in an abnormal way because there is something wrong in the cell’s control centre. You have probably heard of DNA which is the material we inherit from our parents and makes us who we are. Our DNA is coiled up inside all the cells in our body and amazingly, the coil in each cell (often described as a twisted ladder) can be a meter long if stretched out. When talking about DNA and how our body works we also tend to talk about genes. Genes are basically small sections of the DNA ‘twisted ladder’ and it is the genes that carry the ‘codes’ (instructions) for telling our cells what they need to do in order for the body to grow and work properly.

Healthy cells that work properly are told by the genes to divide and make more cells if the body needs more cells to grow or to replace cells that are damaged or cells that have died. But sometimes mistakes happen when the cells divide and the genes pick up these mistakes. We call these mistakes mutations or faults and they happen all the time throughout our lives.

There are various reasons for why these faults happen and we know that some of those reasons are smoking, radiation, chemicals in our environment, sun damage caused by the ultraviolet radiation and also substances that we have in our foods. But these faults also happen naturally in our bodies and then of course there may be reasons that we don’t know about yet.

Usually when faults (mutations) happen in our cells the genes recognise what the fault is and they can manage to repair the fault or instruct the damaged cells to die. Other times our immune system realise that the faulty cells are not normal and the immune system kills them. Therefore our bodies have actually got a really good system so that we are usually protected from faulty cells developing into cancer.

Unfortunately, sometimes the genes that are affected by faults are particularly important for the cell in relation to whether the cell should divide or not. If that happens, the cell doesn’t understand the instructions from the genes or the genes give out wrong instructions so that the cell starts dividing in an uncontrolled way. Once that has happened the faulty cell create more faulty cells because they keep dividing and multiplying and in the end the bundle of faulty cells become cancerous because they grow out of control.

If cancer is caused by faulty genes does that mean that cancer is inherited?

In most cases cancer is NOT inherited. It’s true that cancer develops because of faults in our genes, but most of these gene faults happen during our lifetime and are not faults that were there when we were born. Faults can develop as we get older and our cells get more worn out or because of things we are exposed to in our lives such as tobacco smoke or sunlight. The majority of gene faults are caused by those factors and the damage that occurs in the cells due to these gene faults are not inherited from your parents and they cannot be passed on to your children either.

However, sometimes but much rarer, only about 2-3 % of all cancers, there can be faults (that are linked to cancer) in an egg cell or a sperm cell which means that a baby can be born with a gene fault that is inherited from a parent. It’s important to know that even if someone is born with such a gene fault they won’t necessarily develop cancer but they do have a higher risk of developing cancer than if they didn’t have that gene fault. Cells don’t tend to develop into cancerous cells until they have about 6 specific gene faults and that’s why someone who has inherited only one gene fault doesn’t necessarily develop cancer.

Genetic testing

There is a lot of research going on to find out more about genes and cancer in general and which inherited genes are linked to particular types of cancer. The more we know about this, the more doctors will be able to test if someone has a higher risk of developing cancer. So far, there are only a few genes where there have been developed tests that can show if someone has a particular gene fault that increases their risk of getting cancer. If you are worried about whether cancer ‘runs in your family’ you should talk to your parent about it so that they can ask their doctor. In most cases it is NOT the case. And also, if your parent has a type of cancer where there is a known gene fault that can be inherited, your parent’s doctor will talk to your parent about this and whether there is any reason for anyone in the family to be tested,- if there is a test.

If you want to know more about this you can have a look in Maggie's CancerLinks’s section on cancer and families. Also, you can get in  touch with us here at riprap anytime if you have any queries or just want to talk things through.

Page updated 5 July 2017