DNA fingerprinting, also known as DNA typing, DNA testing or DNA profiling, is a chemical test to establish the genetic makeup of a person or another living thing. The technique was discovered by accident by British geneticist Alec Jeffreys in 1984, after he extracted DNA from cells and fixed it to photographic film. DNA fingerprinting was first used in a police investigation in the U.K. in 1986, and since then millions of people across the world have had their DNA tested during criminal investigations.
What Is DNA?
DNA (deoxyribonucleic acid) is in the nucleus of every cell in the body. It is a chain of chemical compounds called bases, which carry genetic information and tell cells how to grow, function and reproduce.
Two bases join together to create base pairs, of which there are about 3 million in your DNA. The complete set of your compounds is called a genome. More than 99.9 percent of every person's genome is exactly the same. The tiny remainder is what makes one person different from everybody else. The exception is identical twins, whose genomes are 100 percent alike.
How Is DNA Tested?
To get your DNA tested, a sample of cells is taken from your body, for example, via blood, saliva or sweat. Chemicals are added to the sample in the lab to separate the DNA, then it is dissolved in water. A further chemical process creates a unique pattern of stripes called a polymorphism (a little like a barcode), which can be studied and matched against other samples to reveal the unique parts of your genome.
DNA Fingerprinting in Forensics
DNA fingerprinting is used in criminal cases, both to identify perpetrators and exonerate innocent parties, by establishing or ruling out a link between a suspect and a piece of evidence. It can also identify dead bodies that have decomposed so much they are no longer recognizable. When used for forensic science, DNA testing uses probes to target regions of DNA specific to humans, to rule out contamination by additional DNA from other sources, such as bacteria or plants.
DNA has been instrumental in many high-profile criminal cases. In 2000, Illinois Governor George Ryan placed a moratorium on executions after a review of DNA evidence cast doubt upon the cases against several death row inmates in the state. In 2011, Illinois abolished the death penalty.
In Texas, DNA evidence cemented the case against Ricky McGinn, who was convicted of raping and murdering his stepdaughter, and was executed in 2000. When DNA evidence was reviewed as part of one of McGinn's appeals, it confirmed that a hair found on the victim's body belonged to McGinn.
DNA Fingerprinting in Medicine
DNA fingerprinting plays an important role in medicine. It is used to match the tissue of organ or marrow donors with transplant patients, to identify hereditary health conditions, and to help find cures for those conditions. Doctors can also use DNA fingerprinting to design personalized medical treatments for cancer patients. DNA fingerprinting has been used to eliminate lab errors, by making sure a tissue sample has been correctly labeled with the right patient's name.
Other Uses for DNA Fingerprinting
DNA fingerprinting can be used for non-criminal identification, for example, to settle a paternity suit, establish a relationship for inheritance purposes or to reconcile family members separated by war or natural disaster. In agriculture, DNA fingerprinting is used to identify genetically modified plants, improve the effect of disease and insect control and reduce pesticide pollution. Additionally, DNA can be used to prove pedigree in racehorses and other valuable animals.
Home DNA Testing
An increasing number of brands offer home genetic-testing kits for a variety of purposes, for example, to determine your "biological age," predict higher risks of developing a serious condition, such as multiple sclerosis or Alzheimer’s, or even analyze "bioinformatics" to receive personalized health, fitness and wellbeing advice. However, the validity and value of home DNA testing is widely disputed.
- The Guardian: Killer Breakthrough – The Day DNA Evidence First Nailed a Murderer
- The Washington Post: Illinois Governor Wants the State to Revive its Death Penalty for Mass Murderers and People who Kill Police
- Office of the Clark County Prosecuting Attorney: Rickey Nolen McGinn
- NIH National Human Genome Research Center: Deoxyribonucleic Acid (DNA)
- Forensic Magazine: 30 Years of DNA Technology
- NIH National Human Genome Research Center: What is Genomic Medicine?
- US National Library of Medicine National Institutes of Health: Applications of DNA Technologies in Agriculture
- The Guardian: What I Learned From Home DNA Testing