What is a BRCA1 Mutation?

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  • Written By: Jillian O Keeffe
  • Edited By: Angela B.
  • Last Modified Date: 07 October 2019
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BRCA1 is a gene involved in suppressing tumors and is also known as "breast cancer 1, early onset". BRCA1 mutation occurs when the genetic sequence is altered from the norm; the term is most commonly used to refer to a genetic change that means the gene does not produce the correct protein product. BRCA1 mutation plays a major role in the development of breast and ovarian cancer in humans, and can also play a part in other cancers.

The gene itself produces a protein used to repair damaged deoxyribonucleic acid (DNA). When the BRCA1 gene is of a normal type and does not have any deleterious mutations, the protein for which it codes interacts with other cell proteins to fix breaks in the DNA. This interaction is called BRCA1-associated genome surveillance complex. A gene known as BRCA2 plays a role similar to that of BRCA1, and carrying mutations in BRCA2 also increases cancer risk.

The DNA breaks occur through environmental exposure to carcinogens such as natural radiation or when a cell divides. If a BRCA1 mutation exists that is significant enough to affect the action of the protein, this repair does not work as efficiently as it should. The result of a defective gene can be that cells divide uncontrollably, resulting in cancer.


The gene is found on human chromosome 17. It has an essential action in mending split DNA and is also found in chimpanzees, dogs, rats, chickens, mice and cows. More than 1,000 mutations have been recognized in the BRCA1 genetic sequence, many of which are associated with cancer risk.

A person with a harmful BRCA1 mutation is at a higher risk than the general public for breast and ovarian cancers. Men with a defective BRCA1 gene are also affected and are more likely to develop breast cancer than men with a normal BRCA1 gene. BRCA1 mutations are passed down from generation to generation but, because each child only receives one copy of a chromosome from each parent to make up a full complement of two of each chromosome, not every child in a generation will inherit the defective gene.

A BRCA1 mutation accounts for up to 40 percent of breast cancers known to be inherited and about 80 percent of breast and ovarian cancers known to be inherited. Genetic testing is available for people who think they may have inherited a BRCA1 mutation. These tests cost from a few hundred US Dollars (USD) to a few thousand USD in 2011.


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