Genetics and Cancer

The body is made up of billions of tiny cells, each of which contains a copy of our genes. Genes are a set of instructions that control how our bodies develop and function. These genes are arranged in a line along our chromosomes, which are like small, tightly-packed bundles of instructions. All human cells (except for sperm and eggs) contain 23 pairs of chromosomes - 46 chromosomes in total. For each of these chromosome pairs, we inherit one chromosome from our mothers, and one from our fathers.

Occasionally alterations can occur within our genes. This does not usually cause any particular problems, but sometimes gene alterations can make an individual more likely to develop specific health problems. Genetic alterations can either be inherited from our parents via our chromosomes, or they can occur at some stage during our life-time due to external environmental factors.

Cancer is one of the health problems which can occur as a result of alterations in a gene or genes.

Having relatives who have developed cancer can often cause individuals to worry that there is a gene alteration running within their family, and that they too will develop the disease. Unfortunately, however, cancer is very common, and as a general rule most people will have one or more relatives who have developed the disease. The majority of these will be sporadic cancers (they will have occurred by chance). Most cancers occur sporadically (that is, they are not caused by an inherited genetic change), and some cancers occur very commonly: for example, in the UK 1 in 9 women will develop breast cancer during their lifetime. It is therefore not surprising if more than one woman within a family develops breast cancer by chance.

Sometimes these cancers can occur because family members share lifestyle or environmental factors which may lead to an increased risk of developing certain types of cancer. Examples of such factors could include sun exposure, or diet.

Occasionally these cancers occur because there is a gene alteration which is being passed from generation to generation within that family. This is actually fairly uncommon, and only a small percentage of all cancers occur because an individual has inherited a genetic alteration from their parents.

In the next section we take a look at what factors Doctors look for when assessing whether or not an individual has a family history of cancer (this also known as an inherited predisposition).

Next Section >> Inherited Predisposition and Cancer