rs1801260
Morning or evening person
What this position does
CLOCK is a core gene of the circadian machinery that keeps your body on a roughly 24-hour cycle. The variant version is associated with going to bed later and preferring evenings. In an environment of electric light and indoor work, a late clock stops being a preference and becomes a mismatch.
Body clock. Shaped by daylight, and its disappearance indoors. This is one of the variants that differs sharply between human populations, because something in the environment made one version worth having.
Light, dark and sleep
The clock in your body is set by light. It evolved under one sunrise a day and no other bright light at all.
What changed: The screen, the last fifteen years. Light at midnight and an attention market. Smartphone ownership among American adults went from 35 per cent in 2011 to 91 per cent in 2025, which is not enough time for anything in your DNA to have responded.
Why it spread: nobody knows. The frequency difference between populations is real and measured. What the variant was worth having for is not known, and any site that tells you is guessing.
Spiral Staircase, chapter 23: Sleep and the Dark You Have Lost Spiral Staircase is written by the same author as this site.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version AA | You have the earlier-clock version on both copies Associated with earlier bed and wake times on average. |
| One copy AG | You carry one later-clock copy Associated with a later chronotype: later bedtime, harder mornings. |
| Two copies GG | You have the later-clock version on both copies Associated with the latest chronotype at this position. Morning light is the strongest lever on this, far stronger than the genotype. |
Worth knowing. Chronotype is highly polygenic and this is one position among many. Replication has been mixed.
How common each version is
| Ancestry group | G (the effect version) | |
|---|---|---|
| African | 15.2% | |
| American | 23.8% | |
| East Asian | 10.1% | |
| European | 30.5% | |
| South Asian | 38.3% |
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 | AA | AG | GG |
|---|---|---|---|
| African | 483 / 661 | 155 / 661 | 23 / 661 |
| European | 243 / 503 | 213 / 503 | 47 / 503 |
| East Asian | 404 / 504 | 98 / 504 | 2 / 504 |
| South Asian | 190 / 489 | 223 / 489 | 76 / 489 |
| American | 203 / 347 | 123 / 347 | 21 / 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
Katzenberg et al., A CLOCK polymorphism associated with human diurnal preference, Sleep (1998)
Coordinates and allele pair verified against Ensembl GRCh37. Direction of effect verified against VEP protein consequences or 1000 Genomes population frequency. Category: Population adaptation.
Where this fits
Common questions
What is rs1801260?
rs1801260 is a position in the CLOCK gene on chromosome 4. CLOCK is a core gene of the circadian machinery that keeps your body on a roughly 24-hour cycle. The variant version is associated with going to bed later and preferring evenings. In an environment of electric light and indoor work, a late clock stops being a preference and becomes a mismatch.
What does it mean if I have GG at rs1801260?
You have the later-clock version on both copies. Associated with the latest chronotype at this position. Morning light is the strongest lever on this, far stronger than the genotype.
What does it mean if I have AA at rs1801260?
You have the earlier-clock version on both copies. Associated with earlier bed and wake times on average.
How do I find out my rs1801260 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: Population adaptation.