the example below to see how forensic labs match DNA
evidence with DNA from suspects.
DNA are extracted from a blood stain on the victim's
shirt as well as from blood samples taken from thwo
suspects. DNA at very specific locations on 13 pairs
of chromosomes is cut out.
DNA at these
locations contains repeating patterns of four basic
chemicals--represented here by A,T,G, and C.
The 13 pairs
of DNA samples are "unzipped." The length
of each repeating pattern of chemicals is measured.
When the length of all 13 pairs of DNA chains matches
between two samples, the odds are 3 trillion to 1
that the samples did come from the same person.