What Is DNA Testing and Why Is It Useful?

Learn About What DNA Testing Is, Along With Its Several Uses

DNA structure, Illustration. Credit: Ktsdesign/Science Photo Library / Getty Images

Your body is made up of trillions of cells. Inside every one of those cells is a structure called the nucleus, which holds 23 pairs of chromosomes that carry your genetic information. Each chromosome is made up of a long string-like structure. That string-like structure is your DNA, as it is made of a chemical called deoxyribonucleic acid (DNA).

Half of your chromosomes are inherited from your mother and the other half are inherited from your father, for this reason you have 2 copies of every gene.

Humans have around 25,000 genes in total and your DNA is a sequence of these pairs of genes.

Your genes carry information about what makes you, you. All of those pairs of genes add up to make a unique combination, like a code, to tell your body whether to have brown hair, or olive skin, or your great aunt's piercing blue eyes. Your DNA also tells your cells how to behave, when to grow, and when to die.

When a person undergoes a DNA test, those string-like structures are unraveled and read. Since you have more than 6 feet of DNA inside each and every cell (the DNA is tightly coiled up to make up the chromosome, so that it fits inside the nucleus), each cell can hold a lot of genetic information completely unique from anyone else (except for identical twins, who share identical DNAs).

How DNA Testing Is Done

To do a DNA test, a sample of your cells is required. This sample can be from your blood, saliva, skin cells or even the inside of your cheek.

Usually, DNA test samples are taken by a doctor or clinic and sent away to a specialized genetic testing lab where the DNA is separated out from your cells.

For a blood test, a needle and syringe would be required to draw a sample of blood. For the saliva sample, you would spit into a tube. For the cheek swap, scraping the inside of your cheek with a large cotton swab should do the job.

It takes a week or more for results to come back from the lab, as it takes lab technicians time to unravel and read the genetic sequencing along the DNA strand.

Why Would You Need a Test 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.

How Much Does It Cost?

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 a few hundred dollars or less. 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. Accessed on feb 19, 2016

Scitable by Nature Education. Genetics Topic Room. What is DNA. www.nature.com. Accessed on feb 19, 2016

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