If you have learned that you have a BRCA1 or BRCA2 gene mutation, you are likely to have many questions about what this means for you. Genetics is a complex subject, so it’s natural to be confused if this language is new to you. Getting the facts about genes and their functions can help you better understand what it means to have a BRCA gene mutation.


the role of genes in our bodies

What are genes?

 

Role_of_Genes_v2

Our bodies are made of trillions of cells. Inside every cell are structures called chromosomes which contain all of our genes. The only cells in our body that do not have chromosomes are our red blood cells. Genes are the “instruction manuals” for our bodies, determining what we look like and how our bodies will grow and function. Every gene has a specific role. Each gene is made up of a unique piece of DNA that carries our genetic code.

We have two copies of each gene: one copy is inherited from our mother and one from our father. The copy we get from our mother may be different from the one we get from our father.

inheritance diagram genes

The genes we inherit typically work normally, but sometimes the DNA of the gene can get damaged. When this happens we refer to it as a “gene mutation”.

What is a gene mutation?

A gene mutation happens when there is a change or mistake in the DNA of a gene. A mutation can occur randomly in a single cell or can be inherited from either parent.

An inherited gene mutation means that you were born with it and it is found in every cell of your body.

A random gene mutation happens in certain cells over time, often as a result of:

  • an error when a cell divides
  • exposure to environmental factors (chemicals, radiation, etc.)
  • lifestyle factors like smoking, diet, and lack of exercise

A mutation can be harmful, harmless, or even beneficial depending on where it is located in the gene. Mutations happen often but our cells are usually able to repair any damage before it becomes a problem.


the role of BRCA genes

What are BRCA genes?

Researchers have discovered several genes linked to increased risk of breast and ovarian cancer. The most common of these genes are the BRCA1 (BReast CAncer 1) and BRCA2 (BReast CAncer 2) genes.

Both women and men have BRCA genes, in every cell that contains chromosomes. The BRCA genes are known as tumour suppressor genes. They work to repair DNA damage and keep cells growing and dividing normally, particularly in the breasts and ovaries, and prevent cancer from developing.

What is a BRCA gene mutation?

If you have tested positive for a BRCA gene mutation, it means that one of your inherited copies of the BRCA1 or BRCA2 gene does not work properly. As a result, your body’s cells have just one working copy of BRCA. This is a permanent change in the DNA code that puts you at greater risk for breast, ovarian and certain other cancers.

inheritance_diagram_BRCA

In this case the father’s gene carried a BRCA mutation (shown in pink).

Why does a BRCA gene mutation put you at greater risk for cancer?

Not everyone who has an inherited BRCA gene mutation will get cancer. Our cells only need one working copy of the BRCA1 and BRCA2 genes to do their job of repairing DNA damage and keeping cells growing normally. However, if the working gene in one cell becomes damaged over time, the cell no longer has a working BRCA1 or BRCA2 gene which can lead to cancer.


gene mutations and cancer

Cancer develops through a complex process. A single gene mutation in a single cell is not likely to cause cancer. However, an accumulation of gene mutations within a cell can cause it to become cancerous.

Normal cells in our bodies have limited lifespans: they grow, divide and die in a controlled manner. Genes help control these normal cell growth processes. When a cell is damaged beyond repair, certain genes send the signal for cell death.

cell_cycle

 

Sometimes a harmful mutation occurs in a cell and it isn’t repaired. Over time this cell can acquire more gene mutations and can become a cancer cell. Cancer cells grow and divide in an uncontrolled manner and do not die when they should. Some cancer cells like breast cancer or ovarian cancer invade surrounding tissue and form cancerous tumours.cancer_cell_development

In Canada, two of every 5 people will develop cancer in their lifetime. The majority of cancers (70-80%) are sporadic, meaning they happen by chance. Some cancers (10-20%) are familial, meaning they cluster in families for unknown reasons. Familial cancer is thought to be caused by a combination of genetic and environmental factors that interact to increase the risk of cancer. Finally, the minority of cancers (5-10%) are hereditary, meaning they are caused by a gene mutation like BRCA1 or BRCA2 that is passed on from a parent. About 1 in 600 people have a BRCA1 or BRCA2 gene mutation. These gene mutations are rare, even in families where there is a history of cancer.


 

Key points to remember

Genes determine what we look like and how our bodies grow and function.

Almost every cell in our body has two copies of each gene. We inherit one gene copy from our mother and one from our father.

Everyone has BRCA1 and BRCA2 genes. Their role is to repair any damage to our DNA and keep cells growing and dividing normally.

If an abnormal change or mistake, called a mutation, happens in a gene it can stop that gene from working properly.

Both men and women can inherit a BRCA gene mutation from either of their parents. If you have the BRCA mutation, there is a 50% chance you will pass it on to your children.Chromosome

Having a BRCA gene mutation means you may be at higher risk of developing breast, ovarian and certain other cancers; it does not mean you will definitely develop cancer.

BRCA1 or BRCA2 gene mutations are rare. Most cancers are caused by chance rather than by a gene mutation passed on by a parent.

Read understanding cancer risks to learn more.