The organs and tissues of the body are made up of cells. Each cell contains all the biological information that we inherit from our parents. This information is stored in our genes in the center (nucleus) of each cell.

Genes influence the way our bodies develop and work. Different genes have different functions. Some things about our appearance such as our eye color are determined entirely by our genes. But most things are the result of an interaction between our genes and our surroundings. For example, our height and weight are related to the genes we inherit (i.e., someone whose parents are tall is likely to be tall also), but also to our diet, exercise, childhood illnesses, etc.

Genes are grouped together on chromosomes. Each cell has 46 chromosomes arranged into 23 pairs. One chromosome of each pair comes from your mother and the other from your father, so each parent provides you with half of your genes.

The information contained in our genes is written in a "code" made up of four chemicals (bases): adenine, thymine, cytosine, and guanine (in their abbreviated form, A, T, C, and G). These four chemicals, repeated in different combinations, contain all the information our body needs to work. This coded information is called DNA (deoxyribonucleic acid).


Some genes control the creation of new cells, when old cells must die, and the repair of damaged DNA. If these genes develop faults (mutations), they may start to grow in a way that causes cancer to develop.

There are two types of mutations: acquired mutations and inherited mutations. Acquired mutations happen throughout a person's lifetime and cannot be transmitted to his or her children. They can happen by chance when a cell multiplies or because a gene is damaged. Some substances such as cigarette smoke can increase the risk of damage to genes.

Most cancers are caused by an accumulation of acquired mutations throughout a person's life. These are called sporadic cancers.

Inherited mutations are faults in genes that you are born with and are passed down from generation to generation. Inherited mutations that make a cancer more likely to develop are called cancer susceptibility genes. If you inherit these genes, it doesn't mean you will have cancer, but you could have a higher risk.