What Are SNPs - A Simple Guide
A friendly explanation of SNPs, the tiny DNA differences that many consumer tests report, and how they relate to traits.
SNPs are single nucleotide polymorphisms - single letter differences that vary among people. Consumer DNA tests report thousands of them.
Why SNPs matter
- They are common and easy to measure
- Some are associated with traits in research
- They provide a compact summary of genetic variation
A basic SNP record
Most raw files list rsid, chromosome, position, and your genotype. Example:
rs123456 1 123456 AGSNPs and traits
Traits are influenced by many SNPs and by environment. A single SNP rarely tells the whole story. Treat trait indicators as probabilities, not certainties.
For a private way to explore your SNPs and traits, read on device DNA analysis and our browser based walkthrough.
Common terms in plain language
- rsid - a stable identifier for a variant in public databases
- allele - a version of a genetic letter at a position, like A or G
- genotype - your pair of letters at a position, like AG
- minor allele frequency - how common an allele is in a population
How to look up a SNP in your file
rg "^rs429358" my_raw_dna.txt # or: grep '^rs429358' my_raw_dna.txtIf a line appears, you will see the chromosome, position, and your genotype. If nothing appears, that SNP is not included in your file.
A note on context
Many traits depend on groups of variants working together and on non genetic factors. Treat any single result as a small piece of a larger picture.
This guide is educational only.