What is a ‘Cancer Gene’? How Genetic Mutations Lead to Cancer

An estimated 170,000 Australians were diagnosed with cancer in 2025 Cancer Australia. While many people understand that cancer has a genetic component, the precise mechanisms by which our genes – the very blueprints of who we are – can change and contribute to cancer development are often less clear. This article explores the role of genetic mutations in cancer, how these mutations arise, and what can be done to mitigate the risks.

DNA Mutations: The Root of Cancer

DNA, often called the “instructions for life,” provides the code for building and maintaining our cells. This code is organized into genes, each containing the instructions for a specific protein. Proteins are the workhorses of the cell, performing a vast array of functions that keep everything running smoothly.

When errors occur in this instruction manual – these errors are called DNA mutations – it can disrupt normal cellular function. Fortunately, cells have proteins dedicated to identifying and repairing DNA mutations. However, if a mutation cannot be repaired, the cell may produce too much or too little of a particular protein, or a protein that doesn’t function correctly.

A critical pathway to cancer often involves mutations in the genes responsible for repairing DNA mutations. If these repair proteins are non-functional due to their own mutations, other DNA mutations accumulate unchecked.

The Case of BRCA1

BRCA1 is a well-known example of a gene involved in DNA repair. A mutation in the BRCA1 gene can lead to a loss of functional BRCA1 protein, hindering the cell’s ability to correct subsequent DNA errors. This accumulation of mutations can ultimately lead to uncontrolled cell growth and cancer.

One mutation alone might be manageable, but as more accumulate, a cell can lose its ability to regulate growth and avoid programmed cell death (apoptosis). Eventually, this can result in a cell that divides uncontrollably and acquires further mutations – becoming cancerous.

Types of DNA Mutations: Germline vs. Somatic

DNA mutations can occur in two main ways:

• Germline Mutations: These mutations occur in the cells that produce eggs and sperm and can be passed on to children.
• Somatic Mutations: These mutations occur in any other cell type and are not inheritable.

The distinction between germline and somatic mutations is crucial because only germline mutations can be transmitted to future generations.

Inheriting a Genetic Mutation

A somatic mutation in BRCA1, occurring in a single cell, is relatively limited in its impact. However, inheriting a germline BRCA1 mutation means that every cell in the body carries one copy of the faulty gene. While individuals still have one functional copy of BRCA1, the overall risk of developing cancer is significantly increased.

For example, a woman with an inherited BRCA1 mutation has a 65% chance of developing breast cancer and a 39% chance of developing ovarian cancer by age 70 Medical Xpress. In contrast, women with no family history of breast cancer have a 9%–12.5% chance of developing the disease by age 75.

Mutations in another DNA repair gene, BRCA2, also carry similar risks. Men with mutations in either BRCA1 or BRCA2 face increased risks of breast and prostate cancer.

Scientists have identified dozens of “cancer genes” beyond BRCA1 and BRCA2, such as TP53, which plays a role in killing abnormal cells. Inheriting a TP53 mutation is associated with a very high cancer risk, with individuals having a 90% chance of developing some form of cancer by age 60.

What Can Be Done About Cancer Genes?

While you cannot change your genes, understanding your risk is the first step in proactive health management. Leading a healthy lifestyle – avoiding smoking, limiting alcohol consumption, exercising regularly, eating a balanced diet, and protecting yourself from the sun – is crucial.

If you have a family history of cancer, consulting your doctor is recommended. They can assess your risk and discuss the possibility of genetic testing and counseling. For those with inherited genetic mutations, earlier and more frequent cancer screenings or preventative surgeries may be advised.

As with all cancers, early detection remains key to successful treatment.