Acquired and inherited cancer gene variants
Our bodies are made up of tiny building blocks called cells. Inside nearly every cell is a set of genes. Genes are the instructions for your body to work.
If a gene is changed, it may not give the correct instructions anymore. A change in a gene is called a genetic variant or gene mutation.
Over time, genetic variants in a cell may stop the cell working normally. Cancer may develop if cells like this multiply in an abnormal way and grow out of control.
An acquired variant is a gene change that happens during a person's lifetime. This is also called a somatic gene variant.
Acquired variants may happen:
- by chance, when a cell divides or does its job in the body
- because of lifestyle – for example, diet or physical activity levels
- because of things in a person's environment – for example, sunlight or tobacco smoke.
This type of gene change only affects certain cells in the person’s body. It cannot be passed from a parent to child (inherited). A cancer may develop where there are cells with acquired variants. For example, if genes in lung cells are damaged because of smoking, this may eventually allow lung cancer to develop.
A gene change that is passed from parent to child is called an inherited variant or mutation. This type of gene change is there from birth. It is in almost every cell in the person’s body for their whole life.
Some inherited gene variants cause a higher risk of certain types of cancer. The gene variant by itself does not cause cancer. But it may allow other damage to build up faster in cells. This increases the chance that cancer will develop.
Genes are passed from parent to child (inherited) when a sperm and egg join to start a pregnancy (conception).
Each person has 2 copies of each gene. One is from our mother and the other from our father:
- The sperm contains 1 copy of the father’s genes.
- The egg contains 1 copy of the mother’s genes.
You only get 1 copy of each of your parent’s genes. If one parent has a gene variant, you either get the copy with the variant or the copy without the variant.
This means there is a 1 in 2 (50%) chance the gene variant is passed on.
How genes are inherited
If you have the gene variant, there is a 1 in 2 (50%) chance any children you have will inherit it.
Cancer gene variants cannot skip or miss a generation. If one of your parents has a gene variant, there is a 1 in 2 (50%) chance it has passed to you. You either inherit it or you do not. If you do not inherit the variant, you cannot pass it to your children.
Sometimes it can seem like the cancer skipped a generation. This is usually because a person in the family has the variant which is then passed on to their child. But the person does not develop cancer themselves.
This might happen because of the following reasons:
- Having a cancer gene variant raises a person’s risk of developing cancer. But it does not mean they will definitely develop cancer. Sometimes the person does not develop cancer, but their child inherits the variant and does. This can seem like the cancer gene has skipped a generation.
- A person may inherit and pass on a cancer gene variant for a cancer type they cannot develop themselves. For example, gene variants linked to breast and ovarian cancers can pass through the father’s side of the family. A father who inherits this type of variant is unlikely to develop breast cancer and cannot develop ovarian cancer. But they still have a 1 in 2 (50%) chance of passing the variant to their children. If their daughter inherits the variant and develops breast or ovarian cancer, it can seem like the cancer gene has skipped a generation.
If you are worried you may have inherited a cancer gene variant, our information about family history, genes and cancer risk may help. It explains:
- how information about your family history can be used to assess your risk of cancer
- ways to reduce and manage inherited cancer risk
- more about some genetic conditions and inherited cancer syndromes.
We also have information about how the genes in cancer cells can be used to develop or plan cancer treatment. Find out more about:
Below is a sample of the sources used in our family history and cancer information. If you would like more information about the sources we use, please contact us at firstname.lastname@example.org
Monahan KJ, Bradshaw N, Dolwani S, et al. Guidelines for the management of hereditary colorectal cancer from the British Society of Gastroenterology (BSG)/Association of Coloproctology of Great Britain and Ireland (ACPGBI)/United Kingdom Cancer Genetics Group (UKCGG). Gut. 2020; 69: 411–444. Available from DOI: 10.1136/gutjnl-2019-319915 (accessed October 2022).
NICE. Familial breast cancer: classification, care and managing breast cancer and related risks in people with a family history of breast cancer. Clinical guideline [CG164]. Last updated: 20 November 2019. Available from https://www.nice.org.uk/guidance/CG164 (accessed October 2022).
NICE. Molecular testing strategies for Lynch syndrome in people with colorectal cancer. Diagnostics guidance [DG27]. Published: 22 February 2017. Available from https://www.nice.org.uk/guidance/dg27 (accessed October 2022).
NICE. Testing strategies for Lynch syndrome in people with endometrial cancer. Diagnostics guidance [DG42]. Published: 28 October 2020. Available from https://www.nice.org.uk/guidance/dg42 (accessed October 2022).
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Marc Tischkowitz, Reader and Honorary Consultant Physician in Medical Genetics.
Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.
The language we use
We want everyone affected by cancer to feel our information is written for them.
We want our information to be as clear as possible. To do this, we try to:
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You can read more about how we produce our information here.
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