Learn more about how genes can affect your risk of cancer.
Genes.
What are genes.
Genes are how traits can be passed on from parents to their children, such as blue eyes. Genes are arranged one after another on structures called chromosomes.
A chromosome contains a single long molecule called DNA (deoxyribonucleic acid). Each cell within the body contains 23 pairs of chromosomes. One single gene will only make up a small part of a chromosome. Humans have approximately 20,000 genes across all their chromosomes.
DNA is built from blocks called nucleotides. The ‘rungs’ of the ladder in DNA are made up of the nucleotide ‘bases’. They fit together to make pairs, Adenine always matches with Thymine, and Cytosine with Guanine.
We inherit one copy of each chromosome from each parent. The sequence of the bases is used by the cells to make proteins. These proteins perform important functions in keeping cells healthy.
What is a gene mutation.
There are different types of gene mutation. A change in the sequence of a cell’s DNA is called a mutation. There are lots of different ways DNA can be mutated, it may be that one nucleotide is swopped for another or missing.
Mutations can occur as part of aging or for example from exposure to chemical such as tobacco smoke or radiation. These are called ‘somatic mutations’. They are not inherited from our parents.
Mutations can affect how proteins which keep cells healthy or stop them growing uncontrollably. When these proteins are missing or don’t work well they can increase the risk of cancer.
Most cancers are not caused by genetic mutations. But around 1 in 10 cancers are caused by mutations that have been inherited.
How can genes affect my risk of cancer
01 — Mutations
Most cancers occur after several mutations have built up in cells over time. DNA in cells is continually being damaged, this could be from harmful things in the environment such as toxins or smoke. Sometimes errors occur by chance as cells naturally grow and divide.
02 — Inherited mutations
If someone inherits a mutated or ‘faulty’ copy of one gene they are may need fewer mutations during their lifetime before cancer occurs. This is why people who have inherited a cancer risk gene often experience cancers at a younger age.
03 — Breast cancer risk genes
There are many different genes that may impact the risk of breast cancer. They can also be associated with other cancers, especially ovarian cancer. The most common gene is called BRCA, (BReast CAncer gene). There are also lots of others including PALB2, ATM, and CHEK2. Many of the genes code for DNA repair proteins. These are proteins that act as a ‘security guard’ for your DNA. They are constantly monitoring your DNA and when they spot errors they can repair them. If they don't work properly your cells’ DNA mutations build up. The more mutations in a cell’s DNA there is more chance that the cells will start to grow uncontrollably and become cancer.
04 — How do I know if I have a gene mutation
There are many different gene mutations that can affect your risk of cancer. Most people with these genes don’t know about it.
For example, about 1 in 400 people carry a mutation in the BRCA 1 and 2 genes, they are at a high risk of breast and ovarian cancer.
It’s estimated over 97% of people in London with a BRCA mutation do NOT know.
“Knowing my gene mutation gave me so much power.”
Find out more about knowing your genetic risk.
BRCA is the most well-known breast cancer risk gene. My mutation is the PALB2 gene which is much less common.