Burrows-Wheeler Tandem Repeat Searcher (BWtrs) is an on-line application that searches for the exact occurences of tandem repetitions in DNA seqeunces. BWtrs finds tandem repetitions in DNA sequence without prior knowledge of the pattern, its size or number of copies.
A tandem repetition is a pattern of two or more nucleotides that occurs twice (tandem repeat) or more (tandem array) times and the repeated motifs are directly adjacent to each other. Two classes of tandem repetitions, microsatellites and minisatellites, have gained an increasing attention from the scientific community.
Microsatellites or short tandem repeats consist of repetitive variant repeats that range in length from 2 to 10 base pairs. Microsatellites have become the preferred markers in genetic mapping as a result of their relatively uniform distribution, and high degree of polymorphism. A number of genetic diseases such as Huntington's disease, Myotonic Dystrophy, and Fragile X have been found to result from increasing numbers of a particular class of microsatellites, called tri-nucleotide. Microsatellites have been also analyzed for size variation by the polymerase chain reaction (PCR).
Minisatellites are moderate arrays of short tandem repeats (approximately 10 to 100 base pairs) found in the genomes of most eukaryotes. Minisatellite DNA is highly polymorphic and reveals a locus with a great number of alleles that have a high probability of being genetically informative in the great majority of cases. Therefore, minisatellites have been extensively exploited for DNA fingerprinting, one of the most fascinating discoveries in molecular genetics.