Genetic testing detects alterations in DNA or chromosomes. The results of genetic tests can be used to diagnose genetic disease, predict risks of disease, and identify carriers of genetic disease. Human genetic testing requires laboratory analysis of DNA isolated from samples including cells, blood, or amniotic fluid. Once a specific alteration in a gene that correlates with a disease has been identified, scientists develop tests that can distinguish an altered copy of the gene from a copy without the alteration.

One method of identifying alterations in a gene is to sequence the patient’s DNA. Another method is to design molecular probes that attach to the alterations that can be visualized using special methods in a laboratory. A third method for identifying genetic alterations involves functional or biochemical tests, which demonstrate the presence of an altered gene through the presence of abnormal proteins or no proteins at all. Changes in chromosome number or structure, which can cause developmental conditions or diseases, can be tested for as well.

Genetic testing can be done at many different times in one’s life. Diagnostic or confirmatory genetic testing can identify or confirm the diagnosis of a disease or condition. Genetic tests also can be used to determine one’s risk of developing a particular disease or condition, like heart disease or breast cancer, later in life. Genetic tests can be used to determine whether a person will have a certain reaction towards a drug or medication. Adults thinking about having children can undergo carrier screening if they are concerned that they may be at risk to have a child with a genetic disease. Carrier screening determines whether an individual could pass a copy of a disease gene to his/her child. Prenatal genetic testing of a developing fetus during pregnancy can identify an alteration linked to current or future diseases. Genetic testing of newborn babies can identify a genetic disease or condition. Tests that identify molecular changes in DNA and biochemical tests that detect metabolic conditions are used.

Typically state public health programs decide which tests should be offered in order to facilitate early diagnosis and treatment. Preimplantation genetic diagnosis (PGD) following in vitro fertilization can identify embryos with specific genetic characteristics to help determine which embryos to implant into a woman’s uterus to avoid having a child with a genetic disease or to select a child with particular characteristics.

Last updated 5/2006