How to Read Your Raw DNA Data
A look at the raw data files consumer DNA testing services let you download.
If you've taken a consumer DNA test, there's a good chance the service lets you download a raw data file with your results. Those files can look intimidating at first, so here's a plain walk-through of what's actually in them and how they're put together. This is educational reference material, not medical advice — questions about your health and genetics are best talked through with a qualified healthcare professional or genetic counselor.
What the raw file contains
A typical raw data file is just plain text, with each row describing a single position in the genome that the test looked at. Consumer tests don't read your entire genome; instead, they check specific, predetermined positions, usually ones where variation tends to be common or informative. So while the file lists a lot of positions, it still represents only a small slice of the complete genome.
The columns
Each row packs in a few pieces of information. One column is an identifier for the position — it often starts with the letters rs followed by a number, which is the reference identifier used in genetic databases. Other columns tell you the chromosome and where on that chromosome the position sits. The last column shows the genotype: the pair of genetic letters observed there, one inherited from each parent. Those letters are A, C, G, and T.
What a genotype means
At each position you typically have two values, one from each parent, so a genotype might show up as AA, AG, or GG. When the two values match, it's called homozygous; when they differ, it's heterozygous. You can look up the reference identifier for any position in public genetic databases to see what's known about variation there. Worth keeping in mind, though: having a particular genotype doesn't automatically point to any specific outcome.
Limitations and cautions
Raw data from consumer tests comes with real limitations. The testing method can throw occasional errors at individual positions, so no single result should be taken as the final word. The tests also cover only selected positions, not all of your genetic variation. And most importantly, the link between genetics and health is genuinely complex — most traits are shaped by many genes alongside environment and other factors. Interpretations from third-party tools vary a lot in quality, so it's wise to treat them with caution.
Approaching the data responsibly
Exploring raw genetic data can be genuinely interesting, but it's also easy to read too much into it. What a public database says about a specific variant reflects general findings from research — it isn't a personal diagnosis. If you have concerns about a health condition, or you're thinking about acting on something you found in your genetic data, it's a good idea to talk with a healthcare professional or genetic counselor who can weigh it against your full circumstances.
Summary
In short, a raw DNA data file from a consumer test is a text file listing selected genome positions, each with an identifier, a location, and an observed genotype. It covers only part of the genome and can contain errors. It's worth exploring, but reading it accurately is genuinely complex, so for anything health-related it's best to lean on professional guidance.