Glossary
DNA and genetics glossary
Plain-English definitions of the genetics terms you'll see in a DNA health report — SNP, rsID, genotype, MTHFR, methylation, polygenic score, and more.
- SNP (single nucleotide polymorphism)
- A single-letter difference in DNA sequence at a specific position in the genome — the most common type of genetic variation between people. Consumer DNA tests read hundreds of thousands of specific SNP positions.
- rsID
- The reference SNP ID number that uniquely identifies a specific genetic variant, assigned by NCBI's dbSNP database (for example, rs1801133). It's the standard way genetic findings are cited and cross-referenced.
- Genotype
- The specific combination of DNA letters (alleles) a person carries at a given position — for example, CT or TT at a given SNP. A raw DNA file is, at its core, a long list of genotypes at named positions.
- Allele
- One of two or more versions of a DNA sequence at a given position. A person inherits one allele from each parent, so most positions have two alleles per person.
- MTHFR
- A gene that provides instructions for making the MTHFR enzyme, which plays a role in folate (vitamin B9) processing and homocysteine metabolism. Common variants include C677T and A1298C — among the most frequently discussed variants in consumer DNA reports.
- Methylation
- A biochemical process where a methyl group is added to a molecule, including DNA itself. Broadly involved in regulating gene expression and metabolism; the 'methylation cycle' refers to the connected set of reactions that includes MTHFR's role.
- Polygenic score
- A single score estimating genetic predisposition for a trait or condition by combining the small individual effects of many genetic variants together, rather than looking at any one variant in isolation.
- Raw DNA data file
- The unprocessed export of the specific genetic positions a consumer DNA test read, downloadable from your testing provider's account. This is the file DNA Layer's evidence panel reads to build your report — no new test required.
- VCF (Variant Call Format)
- A standard file format for storing genetic variant data, typically produced by whole-genome or whole-exome sequencing rather than consumer genotyping arrays.
- Whole-genome sequencing vs. genotyping
- Genotyping (used by 23andMe, AncestryDNA, MyHeritage, and TellMeGen, though TellMeGen support is newer and less tested) reads a fixed set of hundreds of thousands of known positions. Whole-genome or whole-exome sequencing reads a far larger portion of the genome directly, typically producing a VCF file — support for which is on DNA Layer's roadmap.
See these terms in your own DNA
Upload your raw DNA file and see which of these show up in your personalised health layer, each with its own evidence and citations.
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