<prompt> BRCA1 gene is located on chromosome:17q2113q1212q1321q17  <response>: 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. 