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Variable Number of Tandem Repeats

A Variable Number of Tandem Repeats or VNTR refers to the short nucleotide sequence that spans between 14 to 100 nucleotides long, which is organized into clusters of tandem repeats (hence the name). These tandems are usually repeated for about 4 to 40 times per occurrence. Clusters of these tandem repeats are located all over many chromosomes. Each variant of these clusters are called an allele and they are inherited codominantly.

VNTRs actually have an important role to play in forensic crime investigations when it is used in tandem with polymerase chain reactions. During forensic investigations restriction enzymes are used to cut through the VNTRs and the resulting reaction is then observed through a gel electrophoresis. When this happens, a pattern of bands that are unique to every individual is produced. The number of times that a sequence is repeated would change for every individual and even between the maternal and paternal loci of an individual. This is so accurate because, like fingerprints, the likelihood of two individuals having the same banding pattern on their VNTRs is almost impossible thus it is a fool proof way of proving the guilt of a suspect. This test is also admissible in court.

Web Resources On Variable Number of Tandem Repeats

Chang Bioscience
Examples of VNTR Analysis

Book Resources On Variable Number of Tandem Repeats

Analysis of Triplet Repeat Disorders by D. C. Rubinsztein, M. R. Hayden, Eds.
Forensic Pathology, Second Edition by Vincent J.M. DiMaio, Dominick DiMaio

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