Single Nucleotide Polymorphism (SNP)
Definition
A position in the genome where a single nucleotide varies between individuals. Consumer DTC genomic tests genotype hundreds of thousands of SNPs; SNP profiles are used in IGG because they can be compared across consumer databases in a way that CODIS STR profiles cannot.
- Definition
- A genome position where a single base varies between individuals
- Typical DTC test scale
- Genotypes hundreds of thousands of SNPs
- Forensic use
- Investigative genetic genealogy (IGG)
- Contrast
- Not directly comparable to CODIS STR profiles
Common questions
Why are SNPs used for genetic genealogy instead of the STR markers used in CODIS?+
Consumer genealogy databases like GEDmatch store SNP profiles from direct-to-consumer testing kits, and SNP data supports the distant-relative matching genealogy relies on, while CODIS STR profiles use a different marker system that those databases cannot compare against.
Does SNP-based genealogy searching raise different privacy concerns than STR profiling?+
Yes, because a SNP profile can reveal relatives several generations removed and traits beyond identity, it exposes far more relatives and personal information per search than a CODIS STR comparison, which is why consumer database policies on law enforcement access are closely scrutinized.
Related terms
- Barbara Rae-Venter
- The genetic genealogist who led the family-tree reconstruction in the Golden State Killer investigation. Previously used the same technique to identify an...
- Centimorgans (cM)
- The unit of genetic map distance used to measure shared DNA between individuals. A first-degree relative shares approximately 2,550 cM; a third...
- 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...
- ForenSeq Kintelligence
- A Verogen (formerly Illumina) forensic SNP genotyping kit targeting approximately 10,000 kinship-informative SNPs, designed to generate profiles compatible with consumer genealogy databases...
- GEDmatch
- A consumer genealogy database founded in 2010, used in the Golden State Killer investigation. Changed from opt-out to opt-in for law-enforcement access...
- Genetic Genealogist
- A specialist who combines DNA match data with traditional genealogical record research to reconstruct family trees. In forensic IGG casework, the genetic...
- Investigative Genetic Genealogy (IGG)
- A forensic identification technique that uploads a crime-scene DNA profile to a consumer genealogy database, identifies partial matches suggesting distant family relationships,...
- Opt-in Policy
- The GEDmatch policy adopted in May 2019 requiring database users to affirmatively consent for their profile to be visible in law-enforcement queries,...
- Parabon NanoLabs
- A US company that became the primary commercial provider of forensic IGG casework following the Golden State Killer case, offering the Snapshot...