Forensic testing and Matching of DNA
Testing DNA for identification purposes is a considerably different from testing for screening purposes. The principle is to separate DNA in fragments using enzymes and a replication process called PCR (Polymerase Chain Reaction). The fragments can be separated into bands by chromatography on a silica(?) gel. The pattern produced is unique to an individual provided that enough marker points have been referenced. A marker point is a mapped reference point within the genome of a species. These are in regions of the DNA that do not code for proteins, and therefore do not affect issues of health and body development. These areas are often called "junk" DNA.
An overview of Forensic DNA work is in Philip Reilly's book, Abraham Lincoln's DNA, page 53.
STR - Short Tandem Repeat refers to a repeated stretch