variable number tandem repeats
variable number tandem repeats (VNTR; minisatellite DNA) A family of genetic loci found in eukaryotes consisting of short (15–100 bp) sequences of DNA repeated in tandem arrays; in humans these arrays are typically 1–5 kb long. The alleles for any particular locus all have the same sequence but differ as to how many times the sequence is repeated. VNTR loci contribute to repetitive DNA and have proved valuable in DNA fingerprinting, especially in human forensic science. The VNTR sequences can be released intact from a DNA sample using restriction endonuclease enzymes and identified using gene probes with Southern blotting. Alternatively, the VNTR alleles can be amplified by the polymerase chain reaction, separated by gel electrophoresis, and the resultant patterns compared without the need for special gene probes. Since each VNTR locus typically has many different alleles, the likelihood of two individuals having identical sets of alleles for even a few such loci is very remote. Hence, a DNA sample can be ascribed to a particular person with a high degree of certainty.
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variable number tandem repeats
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variable number tandem repeats