Dictionary of Human Evolution and Biology

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Breast Cancer, Familial, Type 1

Autosomal dominant condition characterized by tumors in female breast tissue. Onset usually in the fourth decade. It is the most common form of cancer among American women, with about 44 000 female (vs. 300 male) deaths annually. The chance of contracting BC are about 13% overall; only about 5-10% of all breast cancers cases are familial, but the penetrance is high: between 80 and 90% with the gene are at high risk. The defective susceptibility gene is BRCA1, a transcription factor gene. At least three more related genes have also been mapped: BRCA2, BRCA3, and BRCA4. One of the features of these cancers is a characteristic loss of heterozygosity (LOH) in chromosomal regions contiguous with the affected gene. The possession of a BRCA1 gene (but not of BRCA2) also increases the probability that a woman will develop ovarian and/or cervical cancer during her lifetime. These BRCA genes normally function to repair radiation-induced breaks in double-stranded DNA. In some breast sarcomas, tumor-generated MDM-2 proteins inhibit the effects of the p53 tumor suppressor gene, permitting additional tumor growth. Although men account for only about 1 of every 150 cases of familial breast cancer, they can pass on susceptibility mutations to daughters.

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