**Core Concept**
The BRCA1 gene is a tumor suppressor gene that plays a crucial role in maintaining genomic stability and preventing cancer development. It is involved in the repair of DNA double-strand breaks through the homologous recombination pathway.

**Why the Correct Answer is Right**
The BRCA1 gene is located on the long arm of chromosome 17 (17q21). This gene encodes a protein that helps to repair damaged DNA by recruiting the RAD51 protein, which mediates the exchange of genetic material between homologous chromosomes. Mutations in the BRCA1 gene can lead to impaired DNA repair, resulting in an increased risk of breast and ovarian cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the BRCA2 gene, not the BRCA1 gene, is located on chromosome 13.
**Option B:** This option is incorrect because while the BRCA1 gene is involved in the repair of DNA double-strand breaks, it is not located on chromosome 15.
**Option C:** This option is incorrect because the BRCA1 gene is located on chromosome 17, not chromosome 22.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that mutations in the BRCA1 and BRCA2 genes are associated with an increased risk of breast and ovarian cancer, and genetic testing can identify these mutations in individuals with a family history of cancer.

**Correct Answer: C. 17q21**