Editing Variable number tandem repeat (section)

==Structure and allelic variation==
[[Image:D1S80Demo.png|thumb|right|350px|{{center|Variations of VNTR (D1S80) allele lengths in six individuals.}}]]

In the schematic above, the rectangular blocks represent each of the repeated DNA sequences at a particular VNTR location.  The repeats are in tandem – i.e. they are clustered together and oriented in the same direction. Individual repeats can be removed from (or added to) the VNTR via [[Genetic recombination|recombination]] or [[DNA replication|replication]] errors, leading to alleles with different numbers of repeats.  Flanking regions are segments of repetitive sequence (shown here as thin lines), allowing the VNTR blocks to be extracted with [[restriction enzyme]]s and analyzed by [[Restriction fragment length polymorphism|RFLP]], or amplified by the [[polymerase chain reaction]] (PCR) technique and their size determined by [[gel electrophoresis]].