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
BRCA1 gene is located on chromosome: 
Select and explain. 
A. 17q21, B. 13q12, C. 12q13, D. 21q17
A: 17q21
Answer: A: 17q21 
Explanation: Mutations in BRCA1 and BRCA2 are responsible for 80% to 90% of "single gene" familial breast cancers and about 3% of all breast cancers. BRCA1 is located on 17q21 BRCA2 is located on chromosome 13q12.