DNA as identification
Almost every part of each strain of human DNA is the same. However, except for identical twins, everyone on earth has certain unique features in their DNA, which can be used as a form of identification.
History
The first DNA analysis technology was restriction fragment length polymorphism (RFLP); later, polymerase chain reaction (PCR) allowed the use of very small
DNA samples. The FBI standard today is short tandem repeat (STI) analysis.
STI analysis
STI analysis uses 13 portions, or loci, of the human genome. The odds that two unrelated people would have the same DNA in all 13 loci are about 1 in a billion.
CODIS
The Combined DNA Index System (CODIS) keeps a record of the STI loci for those convicted of violent or sex crimes. If one of these convicts later leaves DNA at a crime scene, it may be used at trial as evidence.
Other Techniques
Mitochondrial DNA analysis uses DNA from sources that can't be used in STI analysis. Y chromosome analysis allows separation of multiple DNA contributors in a sample.
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