Genes are tiny collections of information located within every cell of the body. It is estimated that there are as many as 30,000 different genes in each cell. A unique sequence of DNA makes up each gene. DNA (deoxyribonucleic acid) is a double-stranded helix of nitrogen-containing molecules. Molecules such as proteins, fats, carbohydrates, and nucleic acids are the building blocks of cells.
Genes control cell functioning including growth rates, how often cells divide, and when cells should live and die by making proteins that perform specific tasks for each cell. Therefore, it is important that each gene has the correct code (instructions) for making its proteins. If it does not the protein will not perform the proper task.
The genetics of breast cancer play an important role because research shows that cancer probably occurs when one or more genes in a cell are damaged or missing (mutated). These genes have instructions that make abnormal proteins or no protein at all. This means that the flow of information to the cell via the proteins is disrupted.
The genetics of breast cancer indicate that gene mutations can occur in two ways: a person is born with mutations or a person develops an alteration in a single breast cell sometime during their lifetime. This mutation is passed on to all of the effected cell's descendants.
Inherited breast cancers occur in about 15% of all breast cancer cases. Most of these cases are associated with mutations on two genes: breast cancer gene one (BRCA1) and breast cancer gene two (BRCA2). As mentioned earlier these genes regulate breast cells so that they grow normally and do not become cancerous. However, abnormalities or mutations in these genes may cause cells to grow out of control - thus creating breast cancer.
Research has made it possible to identify the BRCA1 and BRCA2 genes. This has led to new techniques for detecting, treating, and lowering the risk for developing the disease. Genetic testing is the only way to determine if a person has a mutation on one or both of these genes. However, it is strongly recommended that people consult with a genetic counselor before undergoing genetic testing because a counselor can expertly explain the risks and benefits of genetic testing.
What is the risk of developing breast cancer if there are abnormalities on the BRCA1 and BRCA2 genes? Women who do not have these gene mutations have a 12% risk of developing the disease by age 90. In contrast, women with gene mutations have up to an 85% risk of developing the disease by age 70.
Therefore, women who have a family history of breast cancer in which their mothers, sisters, or daughters have had the disease or many cases of the disease have been diagnosed in other relatives (grandmothers, aunts, or cousins) should consider having genetic testing.
The genetics of breast cancer are not fully understood; however, researchers continue to work on putting the pieces of this deadly puzzle together.