Place of the BRCA1 gene on chromosome 17.
BRCA1 (breast cancer 1, early onset) is a human gene. It is on chromosome 17. Mutations in this gene are associated with a significantly increased risk of breast cancer and ovarian cancer. BRCA1 belongs to the class of tumor suppressor genes, that is, the gene normally counteracts the occurrence of cancer. When turned off, a tumor can occur.
The function of BRCA1 is to help restore DNA damage. The BRCA1 gene encodes a protein that, together with other proteins, constitutes a large protein complex called BASC, an English abbreviation for BRCA1-associated genomic surveillance complex, or a genome that explores DNA in search of DNA damage. In the complex there are also other tumor suppressor genes, DNA damage sensors and proteins that can trigger a signal process. The complex works mainly in recognizing and repairing double stranded fragments of the DNA. Mutations and cancer risks
Certain variations in the BRCA1 gene lead to an increased risk of breast cancer and ovarian cancer. Hitherto hundreds of different mutations have been found that lead to such increased risk. Mutations may be minor abnormalities of one or a few base pairs, which may lead, for example, to an early stop codon, or those which alter an amino acid, which causes the protein to lose its function. There are also large deletions, duplications and complex rearrangements of the gene that lead to job loss.
In all cases, it is a change that eliminates one copy of the BRCA1 gene. There is a strong suspicion that cancer occurs when also the other copy of the gene (for some reason) is turned off, thus completely eliminating the normal function of BRCA1 (repairing DNA damage). Mutations in other genes will then no longer be repaired and eventually lead to the development of cancer cells. This model of successive mutations that first disable one allele of a gene and then the other is called the Knudson hypothesis, to American geneticist Alfred Knudson.
If a woman has such a mutation in one of her two copies of BRCA1, then, according to current estimates, she has 87% chance of getting breast cancer before the 70th year and 44% likely to get her 70th ovarian cancer.
In men, the risk of breast cancer is also slightly increased (compared to men without BRCA1 mutation). In addition, their risk of developing prostate cancer is higher.
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