Short Tandem Repeat

Short tandem repeats ( STR ) (English, about short consecutively occurring repetitions) referred to in genetics repeating short base-pair pattern behind each other in a DNA or RNA strand. These repetitive DNA elements are also referred to as Microsatellites. STR are the DNA motif common currently used for genetic individualization of persons.

STR mostly occur in non-coding regions of the DNA, and include the repeating pattern of base pair sequences ( as ( CATC ) n). These regions are highly polymorphic with respect to the number of repeats, resulting in a large number of variants for each STR locus in the course of evolution. Thus, there is a high probability that two different people in the number of STR repeats. The determination of the length of the two STR alleles of an individual done with the DNA amplification via the PCR and subsequent fragment length measurement by electrophoresis. As a result, two figures are given, the number of repetitions of the motif (eg " TH01 6.9 " means the STR ​​markers TH01 has 6 reps on the first and 9 reps on the second allele of the investigated person). These numerical values ​​are the information that will feed into genome databases.

In practice, several different STR loci are analyzed simultaneously, therefore there exist commercially available systems. The combination of these various systems provides a very high probability of being able to distinguish between two different individuals. Thus providing an in use currently commercially available analysis system 17 simultaneously examined STR systems an average probability of less than 1 in 100 billion in that two unrelated persons accidentally have the same DNA pattern. This high rate of discrimination at the same time technically easier handling due to short amplicon lengths it is owed ​​that STR are the method of choice in the kinship analysis and the creation of track profiles in forensic crime scene investigations.