Markers / Gene
TPMT
One position in this gene is readable from a home DNA test.
Thiopurine sensitivity, TPMT *3C
rs1142345 · chr6:18,130,918 · T/C · evidence: established
The other route to thiopurine toxicity, and the main one in European populations.
| If you carry | What it means |
|---|---|
| No copies | Normal function at this position |
| One copy | One reduced-function copy |
| Two copies | Two reduced-function copies |
| Ancestry group | C (the effect version) | |
|---|---|---|
| African | 6.7% | |
| American | 5.8% | |
| East Asian | 2.2% | |
| European | 2.9% | |
| South Asian | 1.7% |
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