BRCA1 rs1799950: Q356R and DNA Repair
The BRCA1 gene helps protect your genetic information. Its protein works with other proteins to repair damaged DNA, helping prevent errors from accumulating as cells grow and divide [R]. BRCA1 is widely recognized because certain pathogenic variants substantially increase breast and ovarian cancer susceptibility. However, many differences within this gene do not have that effect.
You can explore your result in the free BRCA1 GeneExplorer report.
What Does the BRCA1 Gene Do?
BRCA1 produces a tumor suppressor protein, meaning it helps prevent cells from growing and dividing in an uncontrolled way. Inside the cell nucleus, BRCA1 participates in the response to DNA damage. It works with other proteins to repair breaks and maintain the stability of the cell’s genetic information.
DNA breaks can arise during normal cellular processes or following environmental exposures. Repair systems help cells manage this damage before it is passed on through further divisions [R].
For another important component of this system, read about BRCA2 rs11571833 and rs144848.
What Is BRCA1 rs1799950?
BRCA1 rs1799950 is a missense variant: a DNA difference that changes one amino acid in a protein.'
At position 356, it substitutes:
Glutamine → arginine
The shorthand Q356R describes that substitution:
Q means glutamine.
356 identifies the protein position.
R means arginine.
You may also encounter p.Gln356Arg or c.1067A>G in scientific and clinical sources. The latter uses BRCA1’s coding-sequence notation; GenesUnveiled displays the corresponding forward-strand T/C alleles [R].
TT, CT, and CC: What Do Your Results Mean?
Forward-strand genotype | Protein forms | Interpretation |
TT | Gln/Gln, or Q/Q | No copies of Q356R at this position. |
CT | Gln/Arg, or Q/R | One copy of Q356R. |
CC | Arg/Arg, or R/R | Two copies of Q356R. |
The benign classification applies to this variant. CC is not a high-risk BRCA1 finding simply because it contains two copies [R].
What Have Breast Cancer Studies Found?
A 2005 study examined common BRCA1 variation in 1,715 breast cancer cases and 2,502 controls from the Multiethnic Cohort.
For Q356R, the reported comparisons were:
Comparison | Odds ratio | 95% confidence interval |
CT versus TT | 0.88 | 0.65–1.18 |
CC versus TT | 1.07 | 0.21–5.48 |
The wide interval for CC reflects substantial uncertainty. It would be misleading to present these numbers as proof that CT protects against breast cancer or that CC increases risk.
Did Larger Research Confirm Earlier Associations?
A 2007 British study investigated common variation across BRCA1 and several other cancer-susceptibility genes, using up to 4,474 breast cancer cases and 4,560 controls. Q356R was specifically included because earlier research had suggested a possible association.
The researchers did not confirm the previously reported breast cancer association. Their two-stage design also showed how initially promising signals could weaken when examined in an additional sample [R].
How Q356R Differs From Pathogenic BRCA1 Variants
Certain pathogenic BRCA1 variants prevent production of a functional protein or substantially disrupt its protective role. These changes can cause hereditary cancer susceptibility [R].
If breast or ovarian cancer runs in your family, a healthcare professional or genetic counselor can assess whether comprehensive testing is appropriate. The BRCA1 GeneExplorer report covers this selected marker rather than the entire gene. Our Premium reports offer greater coverage.
Explore Your BRCA1 Result in GeneExplorer
BRCA1 connects everyday DNA maintenance with an important area of cancer genetics. Q356R provides a clear example of why the exact variant—and the evidence behind it—matters more than the gene’s name alone.
Visit the free BRCA1 GeneExplorer report to explore your TT, CT, or CC result. You can analyze your existing raw DNA file in your browser to check whether rs1799950 is available.
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