How DNA Profiling Works

The term "DNA," once used only by scientists, has become an everyday part of our vocabulary. It's almost impossible to be unaware of the impact that the use of DNA has had on everything from the court system to genealogy. It's also nearly impossible to be unaware of the controversy. Now that, theoretically, we could each have a profile that can identify us solely by our DNA, many people are worried about how that profile might be used.

You probably have a good idea of what DNA is -- if not, read How DNA Works for the full story. However, what you may not know is exactly what type of information DNA evidence yields, how it's processed and how it's analyzed. That's where DNA profiling comes in.

scientist examines dna sequencing gel for dna profiling
Roger Tully/Stone/Getty Images
As part of the DNA profiling process, a technician examines DNA sequencing gel.

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­In any situation where DNA may be used, a DNA profile must be created. Also known as DNA or genetic typing, DNA profiling is simply the collection, processing and analysis of VNTRs -- unique sequences on the loci (area on a chromosome). VNTR stands for variable number tandem repeats -- meaning that th­e tandem repeats, or pairs of nucleotides, vary in number. Most DNA sequences in diffe­rent people look too similar to tell apart. After processing, however, VNTRs result in bands that are unique enough to be used for identification. These differences were discovered in 1984 by Dr. Alec Jeffreys, while looking at results of an experiment, using DNA belonging to different family members of one of his lab technicians.

Until 1987 -- when the technique was commercialized -- Jeffreys' lab was the only one in the world doing DNA fingerprinting (the original name for DNA profiling, which was changed due to the confusion with actual fingerprinting).

­Although this sounds simple enough, there are actually several different techniques for creating a DNA profile, and new technology is always emerging. We'll look at these techniques next.