Mutation

Any change in the DNA sequence of a gene. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Although these mistakes occur millions of times each day in our cells, our bodies have sophisticated repair systems that recognise and repair many of these mistakes before they become permanent mutations, helping to protect us from diseases such as cancer.

Mutations can be harmful, beneficial, or have no effect. Harmful mutations that cause a person to have or be at risk of developing a certain genetic disorder or disease, such as cancer, are known as pathogenic variants.

Mutations can be inherited when they occur in the germ cells, also known as germline variations, meaning they are passed down from a parent to their child.

• The BRCA1[link] and BRCA2 [link] mutations are examples of germline pathogenic variants because they are passed down by the parents and increase the risk of developing several types of cancer.

Mutations can also occur during a person’s lifetime, known as an acquired mutation, meaning they are not inherited from their parents.