rs4988235
Digesting milk as an adult
What this position does
Nearly every mammal switches lactase off after weaning. A single change upstream of the lactase gene keeps it on for life, and it spread through Europe in the last ten thousand years alongside dairying.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version GG | Likely lactase non-persistent Two copies of the ancestral version, which is the worldwide majority. Lactase production usually falls after childhood. This is the normal human condition rather than a disorder, and tolerance varies a lot with gut flora and portion size. |
| One copy AG | Likely lactase persistent One copy of the persistence variant is generally enough to keep lactase switched on into adulthood. |
| Two copies AA | Likely lactase persistent Two copies of the persistence variant. Lactase production usually continues at full strength for life. |
Worth knowing. This variant explains lactase persistence in Europe and much of South Asia. Several independent variants do the same job in Africa and the Middle East and are not all on consumer chips, so a non-persistent result in someone of African ancestry is much weaker evidence than it looks.
How common each version is
| Ancestry group | A (the effect version) | |
|---|---|---|
| African | 2.7% | |
| American | 21.6% | |
| East Asian | 0.0% | |
| European | 50.8% | |
| South Asian | 11.3% |
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 | 629 / 661 | 28 / 661 | 4 / 661 |
| European | 154 / 503 | 187 / 503 | 162 / 503 |
| East Asian | 504 / 504 | 0 / 504 | 0 / 504 |
| South Asian | 387 / 489 | 93 / 489 | 9 / 489 |
| American | 219 / 347 | 106 / 347 | 22 / 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.
Where this fits
Common questions
What is rs4988235?
rs4988235 is a position in the MCM6 gene on chromosome 2. Nearly every mammal switches lactase off after weaning. A single change upstream of the lactase gene keeps it on for life, and it spread through Europe in the last ten thousand years alongside dairying.
What does it mean if I have AA at rs4988235?
Likely lactase persistent. Two copies of the persistence variant. Lactase production usually continues at full strength for life.
What does it mean if I have GG at rs4988235?
Likely lactase non-persistent. Two copies of the ancestral version, which is the worldwide majority. Lactase production usually falls after childhood. This is the normal human condition rather than a disorder, and tolerance varies a lot with gut flora and portion size.
How do I find out my rs4988235 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.