rs601338
Secretor status
What this position does
FUT2 decides whether you put blood-group sugars into saliva, gut lining and other secretions. About a fifth of Europeans have two broken copies and are non-secretors, which changes which gut bacteria settle in and which stomach bugs can get a grip.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version GG | Secretor At least one working copy, so you are a secretor. This is the majority. |
| One copy AG | Secretor One working copy is enough. You are a secretor. |
| Two copies AA | Non-secretor Two broken copies. Non-secretors are effectively resistant to the most common strains of norovirus, tend to have measurably different gut flora, and absorb vitamin B12 slightly differently. |
Worth knowing. Resistance is strain-specific. Non-secretors are resistant to the dominant GII.4 strains, not to every norovirus, and not to anything else.
How common each version is
| Ancestry group | A (the effect version) | |
|---|---|---|
| African | 49.1% | |
| American | 34.1% | |
| East Asian | 0.4% | |
| European | 44.1% | |
| South Asian | 28.3% |
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.
How many people carry each result
| Ancestry group | GG | AG | AA |
|---|---|---|---|
| African | 171 / 661 | 331 / 661 | 159 / 661 |
| European | 164 / 503 | 234 / 503 | 105 / 503 |
| East Asian | 500 / 504 | 4 / 504 | 0 / 504 |
| South Asian | 262 / 489 | 177 / 489 | 50 / 489 |
| American | 160 / 347 | 137 / 347 | 50 / 347 |
Counts of people, not modelled frequencies: every one of the 2,504 individuals sequenced by the 1000 Genomes Project phase 3, tallied by the genotype they carry. Deriving these from allele frequencies instead would assume random mating inside each group and undercount the homozygotes.
How to find out which you have
If you have taken a test with 23andMe, AncestryDNA, MyHeritage, Family Tree DNA, TellMeGen or Living DNA, this position is very likely already in the raw data file they gave you. You do not need another test.
One thing to watch if you look it up by hand: testing companies report some positions from one DNA strand and some from the other, and the file does not say which. Read the letters as they appear and you will get the opposite of the truth for some positions. Sequencings resolves that automatically.
Source
Coordinates and allele pair verified against Ensembl GRCh37. Direction of effect verified against VEP protein consequences or 1000 Genomes population frequency. Category: Trait.
Related
- rs602662 — Vitamin B12 levels
Where this fits
Common questions
What is rs601338?
rs601338 is a position in the FUT2 gene on chromosome 19. FUT2 decides whether you put blood-group sugars into saliva, gut lining and other secretions. About a fifth of Europeans have two broken copies and are non-secretors, which changes which gut bacteria settle in and which stomach bugs can get a grip.
What does it mean if I have AA at rs601338?
Non-secretor. Two broken copies. Non-secretors are effectively resistant to the most common strains of norovirus, tend to have measurably different gut flora, and absorb vitamin B12 slightly differently.
What does it mean if I have GG at rs601338?
Secretor. At least one working copy, so you are a secretor. This is the majority.
How do I find out my rs601338 genotype?
If you have taken a home DNA test, this position is very likely in the raw data file you were given. Sequencings reads that file in your browser without uploading it, and resolves which DNA strand each position was reported from, which is the step most manual lookups get wrong.
This is reference information, not medical advice, and not a diagnosis. See the medical disclaimer. Category: Trait.