BRCA1

BRCA1 is a human tumor-suppressor gene whose protein helps repair DNA double-strand breaks and maintain genome stability. Inherited harmful variants increase the risk of breast, ovarian, and several other cancers.

Homologous recombination: A DNA-repair process that uses a matching sequence as a template to repair breaks accurately. BRCA1 helps direct double-strand breaks into this high-fidelity repair pathway.
Hereditary breast and ovarian cancer syndrome: An inherited cancer-predisposition syndrome most often caused by harmful variants in BRCA1 or BRCA2. Germline BRCA1 variants are a major cause of this syndrome.
Mary-Claire King: An American geneticist who helped establish the inherited basis of breast cancer and map BRCA1. Her linkage research helped localize the breast-cancer susceptibility locus later identified as BRCA1.
Two-hit hypothesis: A model in which both copies of a tumor-suppressor gene must be inactivated for a cell to lose its protective function. Many BRCA1-associated tumors acquire a second inactivating event after inheriting one harmful variant.
Variant classification: The process of assigning genetic variants categories based on evidence about their effects on health. Many BRCA1 variants require careful evidence review before risk guidance is possible.
RAD51: A protein that searches for matching DNA sequences and promotes strand exchange during homologous recombination. BRCA1-associated proteins help recruit and regulate RAD51 at damaged DNA.
Germline variant: A genetic change present in reproductive cells and therefore potentially inherited by descendants. Inherited BRCA1 variants are present throughout the body, unlike tumor-acquired changes.
Linkage analysis: A genetic method that tracks inheritance patterns to locate genes near known DNA markers. Researchers used linkage in affected families to map the BRCA1 region.
Loss of heterozygosity: The loss of one parental allele in a cell, leaving the other allele as the remaining copy at a locus. Tumors can lose the functional BRCA1 copy, completing inactivation of the gene.
Penetrance: The proportion of people with a genetic variant who develop the associated trait or disease. Cancer risk among BRCA1 carriers is elevated but not inevitable.

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