DNA fingerprinting is a test to identify and evaluate the genetic information—called DNA (deoxyribonucleic acid)—in a person's cells. It is called a "fingerprint" because it is very unlikely that any two people would have exactly the same DNA information, in the same way that it is very unlikely that any two people would have exactly the same physical fingerprint. The test is used to determine whether a family relationship exists between two people, to identify organisms causing a disease, and to solve crimes.
Only a small sample of cells is needed for DNA fingerprinting. A drop of blood or the root of a hair contains enough DNA for testing. Semen, hair, or skin scrapings are often used in criminal investigations. See a picture of DNA testing in a criminal investigation.
A person who has DNA fingerprinting done voluntarily usually provides a sample of blood taken from a vein. DNA testing also can be done on cells obtained by a simple mouthwash or a swab of the cheeks inside the mouth, but these methods are not recommended.
DNA fingerprinting is done to:
Tell your doctor if you have had a blood transfusion within the past 3 months. You do not need to do anything else before you have this test.
Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?).
DNA that is used to establish paternity is collected from a blood sample. The health professional drawing blood will:
If a DNA blood test is done on a baby, a heel stick will be done instead of a blood draw from a vein.
For a heel stick blood sample, several drops of blood are collected from the heel of the baby. The skin of the heel is cleaned with alcohol and then pricked with a small, sterile lancet. Several drops of blood are collected inside circles on a specially prepared piece of paper. When enough blood has been collected, a gauze pad or cotton ball is placed over the puncture site. Pressure is applied to the puncture site briefly and then a small bandage is usually placed over it.
DNA can be collected from dried blood, skin, saliva, hair, urine, and semen. Bone and teeth samples are used when a body is badly decomposed.
You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain, or have only minor discomfort, after the needle is positioned in the vein. The amount of pain you feel depends on the skill of the health professional drawing the blood, the condition of your veins, and your sensitivity to pain.
The baby may feel a brief sting or a pinch when the lancet pricks the skin. While the blood is being collected, there is very little or no discomfort.
The collection of DNA from saliva, urine, or semen does not cause discomfort.
There is very little chance of a problem from having a blood sample taken from a vein.
There is very little chance of a problem from having a heel stick. A small bruise may develop at the site.
There are no risks linked with collecting DNA from saliva, urine, or semen.
DNA fingerprinting is a test to identify and evaluate the genetic information—called DNA (deoxyribonucleic acid)—in a person's cells.
DNA samples can:
Reasons you may not be able to have the test or why the results may not be helpful include:
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
|Primary Medical Reviewer||Kathleen Romito, MD - Family Medicine|
|Specialist Medical Reviewer||Siobhan M. Dolan, MD, MPH - Reproductive Genetics|
|Last Revised||November 29, 2012|
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