Prof Peter Chantler
Molecular Biology of the Cell
Variable Numbers of Tandem Repeats (VNTRs)
One application of PCR, among many, pertains to its use in the determination of pedigree and uses a form of polymorphic DNA found in so-called minisatellite regions which contain variable numbers of tandem repeats (VNTRs).
Individuals possess regions within their chromosomal DNA that exhibit relatively short repeat sequences. Such repeats can be as short as two nucleotides (eg the dinucleotide sequence 5'..GTGTGT..3'/3'..CACACA..5') or up to several tens of nucleotides in length. For convenience we will illustrate VNTR using a dinucleotide repeat. The number of times that this sequence is repeated varies between different individuals (typically in the range 4-40x) and between maternal and paternal loci of an individual.
Such repeated sequences facilitate the genetic fingerprinting of individuals. For example, an individual may inherit a certain number of repeats at one locus from their mother, and a different number of repeats at the same locus, from their father. Through PCR amplification of material between conserved sites on either side of the VNTR locus, one can obtain a banding pattern of the products on a gel.
This can be done for a number of different loci (3 in this example) and all material can be analyzed on a single gel. By comparing these patterns between individuals, all run on the same gel, one can determine relationships to key individuals.
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Course updated 6 Apr 2004