Variable number tandem repeat

Flanking regions are segments of repetitive sequence (shown here as thin lines), allowing the VNTR blocks to be extracted with restriction enzymes and analyzed by RFLP, or amplified by the polymerase chain reaction (PCR) technique and their size determined by gel electrophoresis.

When removed from surrounding DNA by the PCR or RFLP methods, and their size determined by gel electrophoresis or Southern blotting, they produce a pattern of bands unique to each individual.

When tested with a group of independent VNTR markers, the likelihood of two unrelated individuals' having the same allelic pattern is extremely low.

In analyzing VNTR data, two basic genetic principles can be used: Repetitive DNA, representing over 40% of the human genome, is arranged in a bewildering array of patterns.

VNTRs are a type of minisatellite in which the size of the repeat sequence is generally ten to one hundred base pairs.

Schematic of a Variable Number of Tandem Repeats in 4 alleles.
Variations of VNTR (D1S80) allele lengths in 6 individuals.
Chromosomal locations of the 13 VNTR loci in the CODIS panel.
This shows a theoretical example of a VNTR in two different individuals. A single strand of DNA from each individual is displayed in which there is tandem repeat sequence that the individuals share. The sequence presence is a VNTR because one individual has five repeats, while the other has seven repeats (number of repeats varies in different individuals). Each repeat is ten nucleotides, making it a minisatellite, rather than a microsatellite in which each repeat is 1-6 nucleotides.