How a DNA Test Is Done

For a DNA test, a person usually gives a blood sample; DNA is then taken out of some of the white blood cells. For some DNA tests, a swab of the inside of the cheek may be done, as the DNA can be taken out of the cheek cells. Once the DNA is separated out, scientists hunt for genes along the DNA strand. This type of specialized testing is only done by certain genetic testing laboratories. Usually, DNA test samples are taken by a doctor or clinic and sent away to one of these laboratories. It takes a week or more for results to come back.

Why a DNA Test Is Done

There are several uses for a DNA test:

• testing: Scientists look for a change (mutation) in a particular gene. DNA testing might also be able to identify any family members who have, or are at risk for, developing the genetic disorder.
• Carrier testing: This is to identify family members who have genes that indicate they are at risk for passing on a genetic disorder to their children; these individuals do not have symptoms of the genetic disorder themselves.