BRCA1 and ovarian cancer: However, given the critical role that BRCA2 plays in HR, the effect that germline mutation in BRCA1 or BRCA2 has on increasing a woman’s risk of breast and ovarian cancer and the fact that half the high-grade serous ovarian cancers have defects in HR (27, 44), other SNPs in BRCA1/BRCA2 may have clinical relevance.