This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Breast, Subject name: Pathology
BRCA-1 gene is located at chromosome location 
Select and explain. 
A. 17p2l, B. 17q21, C. 13p21, D. 13q21
B: 17q21
Answer: B: 17q21 
Explanation: Roughly one third of women with hereditary breast cancer have mutations in BRCA1 (at chromosomal locus 17q21.3) or BRCA2 (located on chromosomal band 13q12-13). These genes encode large, complex proteins that do not exhibit close homology to each other or other proteins. Although the molecular basis for their strong association with breast cancer risk is still being elucidated, both BRCA1 and BRCA2 are believed to function in a common DNA repair pathway ref : Robbins Basic Pathology, 9E,page-709