Genetic tests that detect mutations in the BRCA1 and BRCA2 tumor-suppressor genes are widely available. These tests reveal a number of mutations in these genes—mutations that have been linked to familial breast cancer. Assume that a young woman in a suspected breast cancer family takes the BRCA1 and BRCA2 genetic tests and receives negative results. That is, she does not test positive for the mutant alleles of BRCA1 or BRCA2. Can she consider herself free of risk for breast cancer?

Key Concepts

BRCA1 and BRCA2 Genes

BRCA1 and BRCA2 are tumor-suppressor genes that play a critical role in repairing DNA breaks. Mutations in these genes can lead to an increased risk of breast and ovarian cancers. Understanding the function of these genes is essential for assessing genetic risk factors associated with familial breast cancer.

Genetic Testing and Interpretation

Genetic testing for BRCA1 and BRCA2 mutations involves analyzing an individual's DNA to identify specific mutations. A negative test result indicates that the individual does not carry the known mutations, but it does not guarantee freedom from breast cancer risk, as other genetic or environmental factors may also contribute to cancer susceptibility.

Incomplete Penetrance

Incomplete penetrance refers to the phenomenon where not all individuals with a mutation express the associated trait or disease. Even if a person tests negative for BRCA mutations, they may still be at risk for breast cancer due to other genetic factors or lifestyle influences, highlighting the complexity of genetic predisposition.