SNP
Definition
Single Nucleotide Polymorphism. A one-base variant at a defined position. FDP uses SNP panels, not STRs.
- Full form
- Single Nucleotide Polymorphism
- Variation type
- One-base substitution at a fixed position
- Contrast marker
- STR (length-based repeat marker)
- Forensic use
- Phenotype and ancestry prediction (FDP)
Common questions
Why use SNPs instead of STRs for forensic DNA phenotyping?+
STR profiling is built for individual identification through a national database match, not for predicting appearance. SNP panels target specific base positions already linked by research to traits such as eye or hair colour, so they carry the biological signal phenotyping needs that STR length variation does not.
Are SNPs useful for degraded or trace DNA samples?+
Yes. A SNP assay only needs to interrogate a single base, so the amplicon around it can be designed very short. This makes SNP panels more tolerant of degraded, low-template DNA than STR loci, which require longer, intact amplicons to size correctly.
Can a single SNP identify a person the way an STR profile can?+
No. One SNP is only a two-state variant shared by a large fraction of any population, so it has almost no individual discriminating power alone. Identification-grade discrimination requires panels of dozens of SNPs analysed together, and even then interpretation differs from the statistical framework used for STR matches.
Related terms
- Biogeographic Ancestry Inference (BGA)
- Statistical assignment of a donor to continental ancestry groups using Ancestry-Informative SNPs (AIMs). Distinct from racial categorisation.
- Body-Fluid-Specific Transcripts
- RNA markers expressed only in one fluid: HBB for blood, STATH for saliva, PRM1 for semen, MUC4 for vaginal fluid, MMP7 for...
- Deconvolution
- A computational technique that estimates the PSF and inverts its effect to recover a sharper image. The quality depends entirely on how...
- Externally Visible Characteristics (EVCs)
- Traits a witness could see: eye, hair, skin colour, freckling, hair shape, height. The EU-funded VISAGE consortium targets this set.
- Forensic DNA Phenotyping (FDP)
- Prediction of externally visible characteristics, ancestry and age of an unknown donor from SNP genotypes. Investigative lead, not identification.
- HIrisPlex-S
- A 41-SNP externally visible characteristics (EVC) panel for simultaneous prediction of eye, hair, and skin colour, developed at Erasmus MC Rotterdam by...
- mRNA / miRNA
- Messenger and micro RNA. Forensic RNA profiling uses tissue-specific transcripts of both classes to identify body fluids.
- Parabon Snapshot
- A commercial DNA phenotyping service (Parabon NanoLabs, Virginia, US) that genotypes thousands of SNPs from a crime-scene sample and uses machine learning...