VNTR
Definition
Variable Number Tandem Repeats. Longer repeat units (10 to 100 bp) than STRs. The original Alec Jeffreys 1984 fingerprinting markers, now superseded by STRs.
- Full name
- Variable Number Tandem Repeats
- Repeat unit length
- About 10 to 100 base pairs
- Originator
- Alec Jeffreys, 1984
- Current status
- Superseded by STR typing in routine casework
Common questions
Why did STRs replace VNTRs for routine DNA profiling?+
STR repeat units are shorter, so STR loci amplify reliably by PCR from small or degraded samples and can be multiplexed into a single reaction. VNTR analysis relied on RFLP, which needed larger amounts of intact high molecular weight DNA and took much longer to process.
Is VNTR analysis still used anywhere in forensic work?+
It is rarely used for new casework but historical RFLP-VNTR profiles from cases predating STR adoption in the 1990s can still be relevant when re-examining archived evidence or cold cases, sometimes requiring the original technique to interpret the stored data.
Related terms
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- Capillary Electrophoresis
- Size separation of fluorescently labelled PCR products through a polymer-filled capillary on an instrument like the ABI 3500. Output is an electropherogram.
- Chromosome
- A discrete, condensed structure consisting of a single long DNA molecule complexed with histone proteins. Humans normally carry 46 chromosomes in 23...
- CODIS
- The FBI's Combined DNA Index System, the US national STR-based forensic DNA database. Contains profiles from convicted offenders, arrestees, and unidentified crime-scene...
- Multiplex STR Kit
- Single-tube PCR amplifying 15+ STR loci plus amelogenin in one reaction. AmpFISTR Identifiler Plus and PowerPlex are the workhorses in Indian DNA...
- Nucleotide
- The monomer unit of nucleic acids. Each nucleotide consists of a five-carbon sugar (deoxyribose in DNA, ribose in RNA), a phosphate group,...
- PCR
- Polymerase Chain Reaction. Kary Mullis 1983. Exponential amplification of a target sequence using a thermostable Taq polymerase, two primers and thermal cycling.
- RFLP
- Restriction Fragment Length Polymorphism. The first-generation DNA typing method using restriction enzymes and Southern blotting. Required nanograms of intact DNA.
- SNP (Single Nucleotide Polymorphism)
- A position in the genome where the nucleotide base differs between individuals. Genome-wide SNP panels are more powerful than STR panels for...
- 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...
- Watson-Crick Base Pairing
- Adenine pairs with thymine via two hydrogen bonds; guanine pairs with cytosine via three. The pairing rule that makes the double helix...