VNTR (Variable Number Tandem Repeat)
Definition
A tandemly repeated genomic sequence with a longer repeat unit (typically 10, 60 bp) than an STR. VNTRs were used in the first-generation RFLP DNA fingerprinting systems of the 1980s and early 1990s before PCR-based STR typing became practical.
- Repeat unit length
- Typically 10 to 60 base pairs
- Original method
- RFLP, restriction fragment length polymorphism
- Era of use
- 1980s to early 1990s
- Contrast with STR
- Longer repeat unit, needs more intact DNA, not PCR-friendly
Common questions
How did RFLP-based VNTR typing actually generate a profile?+
DNA was cut with restriction enzymes at sites flanking the repeat region, the resulting fragments separated by gel electrophoresis by size, then visualised by Southern blotting with radioactive or chemiluminescent probes, a process that took days to weeks per sample.
Why couldn't RFLP-VNTR handle small or degraded samples the way STR typing does?+
RFLP requires enough high molecular weight, largely intact DNA to survive restriction digestion and produce clean, full-length fragments. Degraded or trace samples common in casework yield fragmented DNA that RFLP cannot resolve, whereas PCR-based STR typing amplifies short, surviving fragments effectively.
Related terms
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- CODIS
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- ESS (European Standard Set)
- The set of STR loci required for profiles entered into EU national databases participating in Prüm cross-border DNA exchange. Currently aligned with...
- Heterozygosity
- The proportion of individuals in a population who carry two different alleles at a locus. A locus with high heterozygosity is more...
- STR (Short Tandem Repeat)
- A genomic locus where a 2, 7 base-pair unit is repeated in tandem a variable number of times between individuals. The variation...