The purpose of this study is to learn more about how chemotherapy affects an individual's thinking abilities (cognition). Some research has shown that chemotherapy can cause changes in cognition in breast cancer survivors. However, it is not clear why this change occurs. In this study, the investigators will look to see if damage to DNA is related to these changes in cognition. Specifically, the investigators want to see 1) if women who have been treated with chemotherapy have more DNA damage than healthy women; and 2) if DNA damage is related to cognitive problems in breast cancer survivors and healthy women.