Short tandem repeat (STR) analysis is a molecular biology method used to compare specific loci on DNA from two or more samples. A short tandem repeat is a microsatellite, consisting of a unit of two to thirteen nucleotides repeated hundreds of times in a row on the DNA strand. STR analysis measures the exact number of repeating units. This method differs from restriction fragment length polymorphism analysis (RFLP) since STR analysis does not cut the DNA with restriction enzymes. Instead, probes are attached to desired regions on the DNA, and a polymerase chain reaction (PCR) is employed to discover the lengths of the short tandem repeats.
STR analysis is a tool in forensic analysis that evaluates specific STR regions found on nuclear DNA. The variable (polymorphic) nature of the STR regions that are analyzed for forensic testing intensifies the discrimination between one DNA profile and another. Forensic science takes advantage of the population's variability in STR lengths, enabling scientists to distinguish one DNA sample from another. For example, the likelihood that any two individuals (except identical twins) will have the same 13-loci DNA profile can be as high as 1 in 1 billion or greater.
- National Commission on the Future of DNA Evidence (July 2002). "Using DNA to Solve Cold Cases" (pdf). U.S. Department of Justice. Retrieved 2006-08-08.