Markers / Gene
MTHFR
2 positions in this gene are readable from a home DNA test.
MTHFR C677T, and why it is oversold
rs1801133 · chr1:11,856,378 · G/A · evidence: established
This is the single most over-interpreted position in consumer genetics. It genuinely does reduce the activity of an enzyme in folate metabolism. What it does not do is most of what the internet says it does.
| If you carry | What it means |
|---|---|
| No copies | You do not carry C677T |
| One copy | You carry one copy, which changes nothing in practice |
| Two copies | You carry two copies, which is common and still changes little |
| Ancestry group | A (the effect version) | |
|---|---|---|
| African | 9.0% | |
| American | 47.4% | |
| East Asian | 29.6% | |
| European | 36.5% | |
| South Asian | 11.9% |
1000 Genomes Project phase 3, via Ensembl, retrieved 2026-09-23. These groupings are coarse and flatten a great deal of internal diversity, particularly within Africa. A variant being common somewhere tells you where a piece of your ancestry probably comes from, and nothing else.
MTHFR A1298C
rs1801131 · chr1:11,854,476 · T/G · evidence: established
The second common MTHFR variant, usually reported alongside C677T. It reduces enzyme activity less than C677T does.
| If you carry | What it means |
|---|---|
| No copies | You do not carry A1298C |
| One copy | You carry one copy, which changes nothing in practice |
| Two copies | You carry two copies, which still changes very little |
| Ancestry group | G (the effect version) | |
|---|---|---|
| African | 15.1% | |
| American | 15.1% | |
| East Asian | 21.9% | |
| European | 31.3% | |
| South Asian | 41.7% |
1000 Genomes Project phase 3, via Ensembl, retrieved 2026-09-23. These groupings are coarse and flatten a great deal of internal diversity, particularly within Africa. A variant being common somewhere tells you where a piece of your ancestry probably comes from, and nothing else.
Where this gene fits
If you have taken a home DNA test, these positions are already in your file.
Read my file