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What Is a DNA Test?

There Are Several Uses for a DNA Test


Updated April 11, 2014

DNA model

Model of DNA

Photo courtesy of NIAID
A DNA test looks at a person's DNA, which carries genetic information in the body’s cells. A gene is a distinct portion of a cell’s DNA.

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:
  • Genetic disorder 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.

  • Paternity testing: This confirms if a child has a similar genetic makeup to a possible father.

  • Crime scene investigation: Forensic investigation teams use special tests to increase the amount of DNA available for examination. The DNA at a crime scene can come from blood cells, sperm cells, or other body cells such as hair or saliva.

  • Ancestry and relationships: DNA from two individuals can be compared to see if they are similar in certain important ways that would mean they are related.

  • Preimplantation DNA test (PGD): This is used to see if an an embryo conceived by in vitro fertilization (IVF) has a genetic disorder. This allows the couple going through IVF to select embryos for implantation that are free of the disorder.

Cost of a DNA Test

The cost of a DNA test depends on what type of testing needs to be done. Some simple tests, like paternity tests or those used for easy-to-detect genetic mutations, might cost about $200. More complicated testing, such as for rare genetic disorders, might cost thousands of dollars.

The National Institutes of Health has an online laboratory directory that allows you to search for labs that offer DNA testing for specific diseases/genes.


Thurmon, Dr. Theodore F. "DNA Testing." Genetics and Louisiana Families. LSU Health Sciences Center. 19 Jun 2009

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