Genetic testing seeks to identify the presence of mutations in genes and chromosomes that have been linked to certain diseases and conditions. Lab technicians screen samples of an individual’s tissue, blood, or saliva for a suspected DNA mutation to confirm a diagnosis or suggest a predisposition to disease. They can also look for the presence or absence of certain proteins that would indicate abnormal gene function. Some tests use short pieces of DNA (called probes) to search for complementary sequences among the 3 billion base pairs of an individual's genome. If a mutated sequence is found, the probe will bind to it and flag the mutation.

The most widespread form of testing for genetic disorders is newborn screening, through which several million newborns in the U.S. alone each year are tested for abnormal or missing gene products. Another form of testing, carrier testing, helps couples learn if they carry a recessive allele for inherited disorders that they might pass on to their children. But the form that attracts the most scrutiny is predictive gene testing, which seeks to identify people at risk of getting a disease before any symptoms are present. Tests are already in use for a range of conditions that include amyotrophic lateral sclerosis (ALS), Alzheimer's disease, inherited breast and ovarian cancers, cystic fibrosis, Huntington's disease, and Tay-Sachs disease. In some cases, lifestyle changes or medical interventions can reduce the likelihood of a disease developing. However, for many genetic disorders, there are no treatment options.

People have many different reasons for taking a genetic test. A negative test result for a person with a family history of genetic disease can offer a sense of relief. If a mutation is found, a person may be able to change certain health habits or receive early treatment to help prevent or slow the onset of disease. Even if there is no treatment option, just knowing about the disease might help people make important planning decisions about their family, insurance coverage, and career.

However, there are reasons why someone might not want to be tested. Current tests cannot entirely assess someone’s disease risk. For example, most diseases are a complex interplay of genetic, lifestyle, and environmental factors. Test results may provide some people with false assurance or needlessly alarm others who might never actually get a disease. If a person learns that he or she is predisposed to a disease for which no cure or prevention exists, that person or his or her family members might fall victim to anxiety or depression. Further, testing positive for the presence of a disease gene might provoke a difficult, life-altering decision: Should the person have preventive treatment, such as radical surgery, to lower the risk of actually contracting the disease? In the case of Catherine Elton, who appears in the video, choosing to test for breast and ovarian cancer genes might have led her to have surgery to remove her breasts and/or ovaries. While some may think that Elton “paid” for her decision—she didn’t test and later developed breast cancer—there are potential “costs” associated with testing as well. In Elton’s mind, the potential costs of rushing into marriage and having children before she was ready outweighed any benefits of testing. Despite her subsequent diagnosis of cancer, Elton does not regret the choice she made.

Genetic disease testing also raises ethical considerations relating to privacy concerns. For example, if you were at higher risk for developing a condition like Alzheimer's disease or breast cancer, while you might want to know about it, how might other members in your family respond when learning of your test results? And what if someone other than you and your doctor could access such highly personal information and use it against your better interests?

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