BRCA Gene Flashcards
What are BRCA1 and BRCA2?
BRCA1 and BRCA2 are human genes that produce tumor suppressor proteins.
What do these protiens do
These proteins help repair damaged DNA and, therefore, play a role in ensuring the stability of the cell’s genetic material.
When either of these genes is mutated, or altered, such that its protein product either is not made or does not function correctly, DNA damage may not be repaired properly. As a result, cells are more likely to develop additional genetic alterations that can lead to cancer.
What precent of breast Cancers are cause by BRCA 1 20 - 25 %
How about Ovarian cancer
Together, BRCA1 and BRCA2 mutations account for about 20 to 25 percent of hereditary breast cancers (1) and about 5 to 10 percent of all breast cancers (2). In addition, mutations in BRCA1 and BRCA2 account for around 15 percent of ovarian cancers overall
What is the probability of inheriting a gene when one of the parents has it
Each child of a parent who carries a mutation in one of these genes has a 50 percent chance (or 1 chance in 2) of inheriting the mutation.
How much does having a BRCA1 or BRCA2 gene mutation increase a woman’s risk of breast and ovarian cancer?
Breast cancer: About 12 percent of women in the general population will develop breast cancer sometime during their lives (4). By contrast, according to the most recent estimates, 55 to 65 percent of women who inherit a harmful BRCA1 mutation and around 45 percent of women who inherit a harmful BRCA2 mutation will develop breast cancer by age 70 years (5, 6).
BRCA 1 = 55 - 65%
BRCA 2 = 45%
Ovarian cancer: About 1.3 percent of women in the general population will develop ovarian cancer sometime during their lives (4). By contrast, according to the most recent estimates, 39 percent of women who inherit a harmful BRCA1 mutation (5, 6) and 11 to 17 percent of women who inherit a harmful BRCA2 mutation will develop ovarian cancer by age 70 years
BRCA 1 = 39 %
BRCA 2 = 11 - 17 %
What other risk factors are there
It is also important to note that other characteristics of a particular woman can make her cancer risk higher or lower than the average risks. These characteristics include her family history of breast, ovarian, and, possibly, other cancers; the specific mutation(s) she has inherited; and other risk factors, such as her reproductive history. However, at this time, based on current data, none of these other factors seems to be as strong as the effect of carrying a harmful BRCA1 or BRCA2 mutation.
What other cancers can because by these genes
Harmful mutations in BRCA1 and BRCA2 increase the risk of several cancers in addition to breast and ovarian cancer.
BRCA1 mutations may increase a woman’s risk of developing
- Fallopian tube cancer and
- Peritoneal cancer
- Men with BRCA2 mutations, and to a lesser extent BRCA1 mutations, are also at increased risk of male breast cancer
- Men with harmful BRCA1 or BRCA2 mutations have a higher risk of prostate cancer
- Men and women with BRCA1 or BRCA2 mutations may be at increased risk of pancreatic cancer (11 ).
- Mutations in BRCA2 (also known as FANCD1), if they are inherited from both parents, can cause a Fanconi anemia subtype (FA-D1), a syndrome that is associated with childhood solid tumors and development of acute myeloid leukemia (12, 13).
- Likewise, mutations in BRCA1 (also known as FANCS), if they are inherited from both parents, can cause another Fanconi anemia subtype (14).
Are mutations in BRCA1 and BRCA2 more common in certain racial/ethnic populations than others?
Yes. For example, people of Ashkenazi Jewish descent have a higher prevalence of harmful BRCA1 and BRCA2 mutations than people in the general U.S. population. Other ethnic and geographic populations around the world, such as the
- Norwegian
- Dutch
- Icelandic peoples, also have a higher prevalence of specific harmful BRCA1 and BRCA2 mutations.
Who should consider genetic testing for BRCA1 and BRCA2 mutations?
- Breast cancer diagnosed before age 50 years
- Cancer in both breasts in the same woman
- Both breast and ovarian cancers in either the same woman or the same family
- Multiple breast cancers
- Two or more primary types of BRCA1- or BRCA2-related cancers in a single family member
- Cases of male breast cancer
- Ashkenazi Jewish ethnicity
Should children be tested
Professional societies do not recommend that children, even those with a family history suggestive of a harmful BRCA1 or BRCA2 mutation, undergo genetic testing for BRCA1 or BRCA2. This is because no risk-reduction strategies exist for children, and children’s risks of developing a cancer type associated with a BRCA1 or BRCA2 mutation are extremely low. After children with a family history suggestive of a harmful BRCA1 or BRCA2 mutation become adults, however, they may want to obtain genetic counseling about whether or not to undergoing genetic testing.
Why should individuals speak with a genetic counselor before getting testing
¥ A hereditary cancer risk assessment based on an individual’s personal and family medical history ¥ Discussion of:
¥ The appropriateness of genetic testing ¥ The medical implications of a positive or a negative test result ¥ The possibility that a test result might not be informative ¥ The psychological risks and benefits of genetic test results ¥ The risk of passing a mutation to children
¥ Explanation of the specific test(s) that might be used and the technical accuracy of the test(s)
What does a positive BRCA1 or BRCA2 genetic test result mean?
¥ If a person learns that he or she has inherited a harmful BRCA1 or BRCA2 mutation, this will mean that each of his or her full siblings has a 50 percent chance of having inherited the mutation as well.
What does a negative BRCA1 or BRCA2 test result mean?
A negative test result can be more difficult to understand than a positive result because what the result means depends in part on an individual’s family history of cancer and whether a BRCA1 or BRCA2 mutation has been identified in a blood relative.
If a close (first- or second-degree) relative of the tested person is known to carry a harmful BRCA1 or BRCA2 mutation, a negative test result please comment
Ifa close (first- or second-degree) relative of the tested person is known to carry a harmful BRCA1 or BRCA2 mutation, a negative test result is clear: it means that person does not carry the harmful mutation that is responsible for the familial cancer, and thus cannot pass it on to their children. Such a test result is called a true negative. A person with such a test result is currently thought to have the same risk of cancer as someone in the general population.
If the tested person has a family history that suggests the possibility of having a harmful mutation in BRCA1 or BRCA2 but complete gene testing identifies no such mutation in the family, a negative result please comment?
If the tested person has a family history that suggests the possibility of having a harmful mutation in BRCA1 or BRCA2 but complete gene testing identifies no such mutation in the family, a negative result is less clear. The likelihood that genetic testing will miss a known harmful BRCA1 or BRCA2 mutation is very low, but it could happen. Moreover, scientists continue to discover new BRCA1 and BRCA2 mutations and have not yet identified all potentially harmful ones. Therefore, it is possible that a person in this scenario with a “negative” test result actually has an as-yet unknown harmful BRCA1 or BRCA2 mutation that has not been identified.
