Breast Cancer Susceptibility Screening Essay

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Breast Cancer Susceptibility Screening


In 1994, researchers isolated a gene, BRCA1, that has had an unprecedented impact on the study of cancer genetics. BRCA1 is a breast cancer susceptibility gene, meaning that women who possess certain mutations in this gene also possess a greatly inc reased risk of acquiring familial breast cancer. Just a year later, a second breast cancer susceptibility gene, BRCA2, was discovered. Mutations in these two genes alone appear to be responsible for approximately 70% of breast cancer cases in families w ith an inheritance pattern affecting several generations.

Due to the impressive statistics and the potential to alter the lives of millions of women, BRCA1 and BRCA2 have
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When proto-oncogenes are activated by either point mutation, amplification, or translocation, they become oncogenes. This activation step often leads to uncontrollable cell growth and formation of tumors. Even so, proto-oncogenes are rarely involved in breast cancer and other hereditary cancers. The second class of regulatory genes, tumor suppressor genes, code for proteins that restrict uncontrollable cell growth. They can be inactivated through loss of expression, deletion, or mutation. Such mutations have the ability to be passed from generation to generation, producing an inherited susceptibility to cancer. Both BRCA1 and BRCA2 are believed to be of this second type, tumo r suppressor genes. As a result, they inhibit tumor formation when functioning normally but cause a predisposition to breast cancer when mutated.

As already mentioned, BRCA1 was the first breast cancer gene to be isolated. This was accomplished through positional cloning methods. BRCA1 is located on the long arm of chromosome 17 and encodes a large, negatively charged protein. A woman who c arries an inherited mutation in BRCA1 has a greater than 80% chance of developing breast cancer at some point in her life. The risk for women in the general population who do not carry a mutation is only 10%. It is important to note, however, that breas t cancer is not inevitable just

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