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How is genetic testing done?

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Once a person decides to proceed with genetic testing, a medical geneticist, primary care doctor, specialist, or nurse practitioner can order the test. Genetic testing is often done as part of a genetic consultation.

Genetic tests are performed on a sample of blood, hair, skin, amniotic fluid (the fluid that surrounds a fetus during pregnancy), or other tissue. For example, a procedure called a buccal smear uses a small brush or cotton swab to collect a sample of cells from the inside surface of the cheek. The sample is sent to a laboratory where technicians look for specific changes in chromosomes, DNA, or proteins, depending on the suspected disorder. The laboratory reports the test results in writing to a person’s doctor or genetic counselor, or directly to the patient if requested.

Newborn screening tests are done on a small blood sample, which is taken by pricking the baby’s heel. Unlike other types of genetic testing, a parent will usually only receive the result if it is positive. If the test result is positive, additional testing is needed to determine whether the baby has a genetic disorder.

Before a person has a genetic test, it is important that he or she understands the testing procedure, the benefits and limitations of the test, and the possible consequences of the test results. The process of educating a person about the test and obtaining permission is called informed consent.

For more information about genetic testing procedures:

Scientific Testimony, an online journal, provides an introduction to DNA testing techniquesThis link leads to a site outside Genetics Home Reference. written for the general public.

The National Genetics and Genomics Education Centre of the National Health Service (UK) offers an overview of what happens in the laboratoryThis link leads to a site outside Genetics Home Reference. during genetic testing.

The Genetic Science Learning Center at the University of Utah provides an interactive animation of DNA extraction techniquesThis link leads to a site outside Genetics Home Reference..

Next: What is informed consent?

Published: February 1, 2016