What is DNA testing and how does it work?
(Lansing State Journal, September 27, 1995)

DNA is a long chain of molecules that encodes our body's blueprint.  Each chain contains long sequences of four different chemicals called nucleotides as the letters of a four letter alphabet.  Certain groupings of these nucleotides spell out a :word:; each "word" gives instructions to the cells in our body.

Every day, our body reads these instructions millions of times, allowing us to grow, think and live our lives.

Each cell in our body contains its own complete set of DNA, and each person in the world has his or her own unique set.

DNA testing is a way to compare people's DNA.  It is frequently used to determine how people are related or to help solve a crime.  Suppose you find a tiny amount of DNA (from say, blood on the back of a leather glove) at a crime scene.  Scientists mix the DNA with chemicals called restriction enzymes.  These enzymes will cut the long chains of DNA into pieces.  The length and number of pieces depend upon the order of the individual nucleotides.  Once cut, each person's DNA gives a unique set of differently sized pieces.  So if you find a suspect whose DNA cuts differently than the DNA found at the crime scene, you can eliminate that person as a suspect.

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