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These days, crime scene detectives look for fingerprints that are more than skin deep. The patterns they seek are “DNA fingerprints,” or sequences of A, G, T and C in the genetic code that are unique to every person. Clues as tiny as a speck of sweat or a strand of hair can provide a genetic “calling card” with enough DNA to identify a suspect. Such evidence can also help innocent people overturn wrongful convictions.
What is a DNA fingerprint?
At a crime scene, detectives search for standard fingerprints as well as evidence containing DNA. Instead of swirled line patterns from skin, a DNA fingerprint shows a pattern of A, G, T and C units, seen only through molecular analysis of a DNA sample. Every individual organism, from a whale to a daisy, has its own unique DNA fingerprint that forms when DNA is passed down from parents to offspring.
In the human genome, roughly 3.2 billion units of DNA code, about one out of a thousand A, T, G, C bases differs from person to person. An “A” might be replaced by a “C” along the code, for instance, creating a “signature” arrangement. Investigators identify individuals using combinations of unique sequences.
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