The BRCA genes are related to breast cancer;​

A) ​women with these genes are about 20 times as likely to develop breast cancer as women without them.
B) ​women with mutated forms of these genes are vulnerable to breast cancer.
C) ​these genes are responsible for about 50% of breast cancer cases.
D) ​women with these genes will develop breast cancer, and 40% of them will do so before age 35.

The statement "women with mutated forms of these genes are vulnerable to breast cancer" accurately summarizes the relationship between the BRCA genes and breast cancer. While women with these genes are at an increased risk of developing breast cancer, having the gene mutation does not guarantee that a woman will develop breast cancer. Additionally, not all breast cancers are caused by BRCA mutations as indicated by choice C. Choice A is not entirely accurate as the exact risk increase varies based on other factors such as family history, age at diagnosis, and other genetic mutations. Choice D is incorrect as not all women with these genes will develop breast cancer and the age of onset can vary.