Forbes
Quora, Contributor
April 7, 2017
Probably the most concerning misconception that people may have about genetic testing is that it is deterministic. There are actually very few genetic diseases that are fully deterministic. The genetics term for this is penetrance. In Huntington Disease (HD), for example, everyone that has a mutation in the HD gene will eventually develop HD. Therefore, we say that HD is 100% penetrant. Most “high impact” genetic diseases have incomplete penetrance. Women with a BRCA1 mutation have ~80% lifetime risk of developing breast cancer, but 20% of women with a BRCA1 mutation never develop breast cancer. This variable penetrance can be confusing, but it’s actually good news, it means that often there are things you can do to reduce your risk of developing the disease. Genetics is (usually) not deterministic.