Frequently asked questions
What is DNA?
Deoxyribononucleic acid (DNA) is a long, double-stranded molecule that looks similar to a twisted rope ladder or double helix.
Sometimes referred to as the blueprint of life, DNA is the fundamental building block for a person's entire genetic makeup. When sperm and egg unite, equal amounts of DNA from each parent combine. This combined DNA determines that person's characteristics.
DNA is found in virtually every cell in the human body. A person's DNA is the same in every cell. For example, the DNA in a man's blood is the same as the DNA in his skin cells, semen, saliva, and the roots of his hair.
DNA is a powerful tool for identifying individuals because it is highly discriminating. Each person's DNA is unique to them. Identical twins are the only exception as they share the same DNA.
Using modern technology, a person's DNA can be extracted from a small biological sample, such as a few drops of blood. This sample can be analyzed, creating a DNA profile that can be used in much the same way as fingerprints are used to identify a person.
A known DNA profile, drawn from an identified biological sample, can be compared to another unknown DNA profile drawn from a different biological sample. If the profiles match, the two samples come from the same person. If the profiles do not match, the samples come from different people.
DNA collected from a crime scene can either link a suspect to the evidence, or eliminate a suspect. It can also identify a victim through DNA from close relatives. Evidence from one crime scene can be compared with evidence from another to link to the same perpetrator whether the crime took place locally, across the country, or around the world.
The DNA molecule is also very stable. This means usable DNA can often be found on evidence that is decades old.
The stability of the DNA molecule when combined with the discriminating features of each individual's DNA, and the accuracy of current DNA analysis techniques, make DNA evidence a valuable and reliable forensic tool.
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