Angelina Jolie's announcement today that she recently underwent a preventive double mastectomy to reduce her risk of breast cancer made big news on TV, in print and on the Web. While Jolie revealed that her decision and procedure were initially  kept private, she says that she is now talking about the issue to raise awareness about the kinds of tests and procedures that are available to all women who want to reduce their risk of both breast and ovarian cancers.

Her decision certainly has people talking. And one of the biggest questions that we all seem to be asking is what exactly is BRCA1? Here is a primer on the gene that influenced Jolie's decision:

What is BRCA1?

Your body has two types of tumor-suppressing genes in breast tissue: BRCA1 and BRCA2. Under normal conditions, those cells stabilize DNA and prevent the growth of tumors. But mutations in either one of these genes can lead to the development of breast or ovarian cancer.

What does BRCA1 stand for?

Breast cancer susceptibility gene 1. (BRCA2 stands for breast cancer susceptibility gene 2.)

How does BRCA1 affect a person's risk of cancer?

According to the National Cancer Institute, "a woman’s lifetime risk of developing breast and/or ovarian cancer is greatly increased if she inherits a harmful mutation in BRCA1 or BRCA2.  BRCA1 mutations may also increase a woman’s risk of developing cervical, uterine, pancreatic, and colon cancer." The risk is highest for women with a family history of breast or ovarian cancer. In Jolie's case, her mother, Marcheline Bertrand, passed away from ovarian cancer at age 56.  

From the website:

"According to estimates of lifetime risk, about 12.0 percent of women (120 out of 1,000) in the general population will develop breast cancer sometime during their lives compared with about 60 percent of women (600 out of 1,000) who have inherited a harmful mutation in BRCA1 or BRCA2. In other words, a woman who has inherited a harmful mutation in BRCA1 or BRCA2 is about five times more likely to develop breast cancer than a woman who does not have such a mutation."

Men with  BRCA1 mutations also have an increased risk of breast cancer as well as pancreatic cancer, testicular cancer, and early-onset prostate cancer. 

How do I know if I have a harmful BRCA1 mutation?

A simple blood test performed at a hospital or doctor's office can help detect BRCA1 and BRCA2 mutations. Results take several weeks to come back and testing can cost anywhere from several hundred to several thousand dollars. Check with your insurance company first about whether or not your insurance will cover the cost. In her op-ed in the New York Times, Jolie acknowledged that the cost of this test "remains an obstacle for many women."

Who should get genetic BRCA1 testing?

According to the Centers for Disease Control and Prevention, only women with increased risk from family history are likely to benefit from such genetic testing for BRCA1 or BRCA2 mutations. Only 3- 5 percent of women who develop breast cancer have a BRCA mutation, and about 10-15 percent of women with ovarian cancer have a BRCA mutation.  

Related on MNN: 'Smart bra' finds breast cancer long before a mammogram

What is the BRCA1 gene?
Angelina Jolie had a double mastectomy because of a mutation in her BRCA1 gene. What is this gene and how does it affect your cancer risk?