Markers / Gene
CHRNA3
One position in this gene is readable from a home DNA test.
How many cigarettes a day, if you smoke
rs1051730 · chr15:78,894,339 · G/A · evidence: established
Sitting in the same nicotine receptor cluster as the dependence variant, and inherited with it. Its effect is measured directly in cigarettes per day, and through that in lung cancer and emphysema risk. Nothing about this was shaped by evolution: tobacco arrived a few hundred years ago and found a receptor system built for something else.
| If you carry | What it means |
|---|---|
| No copies | You do not carry it |
| One copy | You carry one copy |
| Two copies | You carry two copies |
| Ancestry group | A (the effect version) | |
|---|---|---|
| African | 8.7% | |
| American | 21.6% | |
| East Asian | 2.7% | |
| European | 36.9% | |
| South Asian | 18.3% |
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