Final answer:
Having a marker for BRCA1 indicates an increased risk of breast and ovarian cancer; specifically, a 55 to 65% chance of developing breast cancer by age 70. It does not guarantee cancer will occur, but allows for personalized medical care and increased surveillance.
Step-by-step explanation:
A woman who has been told that she has a marker for BRCA1 means that she possesses a genetic variation that is associated with an increased risk of developing breast and potentially ovarian cancer. However, this does not mean she will inevitably get cancer; it simply raises her risk. The exact risk can vary, but 55 to 65% of women with a harmful mutation in the BRCA1 gene will develop breast cancer by age 70, which is significantly higher than the 12% risk for the general population enetic testing and counseling provide valuable information for the individual and their healthcare provider. If a mutation is identified, the patient might undergo more frequent screenings for breast and ovarian cancer, facilitating earlier detection and potentially more effective treatment options. Furthermore, understanding one's genetic predisposition to certain cancers helps in personalizing medical care and preventative strategies. Rebecca's case illustrates why a family medical history review and genetic counseling are crucial when there's a high incidence of cancer in a family. Inherited mutations like those in the BRCA1 and BRCA2 genes, despite being dominant, are not passed to every family member, and other factors, such as environmental influences, also play significant roles in cancer development. Genetic counselors are adept at interpreting test results and guiding individuals through the implications for their health and family planning.