You downloaded your raw DNA file. Now what?

Every major DNA testing company lets you download your raw data. Most people never do, and most who do open the file once, see an endless wall of text, and close it. Fair. But that file is the most information-dense thing you own about your body, and reading it is less mysterious than it looks.

What is actually in the file

Unzip it and you get a plain text table, one row per genetic marker, usually 600,000 to 700,000 rows. Every provider uses the same basic four columns:

# rsid       chromosome   position    genotype
rs762551     15           75041917    AA

Reading left to right: the marker's name (an "rs" number, the universal ID used in research papers), which chromosome it sits on, its exact position there, and your genotype, the two letters you inherited, one from each parent.

That single example row is real, and it happens to matter: rs762551 sits in CYP1A2, the gene for the main liver enzyme that breaks down caffeine. A/A there is the fast-clearance genotype; carrying a C is the slow lean. One row down, 599,999 to go.

The three traps

If you start looking up rows yourself, three things will bite you sooner or later:

• Strand flips. Providers sometimes report the opposite DNA strand for a marker, so a genotype listed in a paper as A/G can appear in your file as T/C: the same result, chemically mirrored. Naive lookup gets this wrong silently.
• Builds. The "position" column depends on which reference genome version the provider used (GRCh37 versus GRCh38), so the same marker has different coordinates in different files. Match on the rs number, not the position.
• No-calls and rare-variant errors. Some rows read "--", meaning the chip failed to read that spot, and rare scary-looking variants in chip data are usually false: when researchers checked chips against real sequencing, more than 8 in 10 calls of very rare variants were wrong. We wrote up why: Chip or full sequence.

What the file is good for

Used well, the raw file is a free upgrade on the test you already paid for. The same data that produced your ancestry pie chart holds your caffeine clearance, chronotype leans, and dozens of other replicated wellness markers the original report never mentioned. You can look markers up one by one on public databases like dbSNP, mind the traps above, and read the studies yourself. It is genuinely doable, and for a weekend of curiosity we recommend it.

The one thing we would tell you not to do: upload the whole file to any site that asks for it casually. A raw genome cannot be changed after a leak, and most upload services store it. Read the privacy policy first, or better, prefer tools that do not take the file at all. That is how Helisoma works: the file is parsed in your browser, only the markers our reports use ever leave your device, and the raw file goes nowhere.

If you would rather not spend the weekend cross-checking strand flips, that is the product: add the file you already have, and get every replicated, honestly-sized finding in it, each one linked to its study, ready to discuss with your AI assistant.