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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.
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
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
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
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
DNA samples can:
Reasons you may not be able to
have the test or why the results may not be helpful include:
Other Works ConsultedFischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
November 29, 2012
Kathleen Romito, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics
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