In 2017, theNobelPrize inPhysiology orMedicine was awarded to threeAmerican scientists —JeffreyHall,MichaelRosbash, andMichaelYoung — for discovering the molecular mechanisms of circadian rhythm.They decoded how cells 'know' what time it is.Inside every cell of your body, molecular clocks are running — feedback loops of proteins and genes that synchronise cellular processes with the daily cycle.
What we call being a 'morning person' or a 'night owl' is not a habit or upbringing.It is a chronotype: the genetically determined phase of your internal clock.People with an early chronotype are biologically comfortable falling asleep and waking earlier.People with a late chronotype — later.And this difference is written into theirDNA.
TheCLOCK gene (CircadianLocomotorOutputCyclesKaput) is one of the primary regulators of circadian rhythm.Together with theBMAL1 gene, it forms a transcription complex that initiates the expression of 'clock' genes —PER1,PER2,PER3,CRY1,CRY2.These genes, in turn, suppressCLOCK/BMAL1 activity, creating a feedback loop with a period of approximately 24 hours.
The polymorphism rs1801260 in theCLOCK gene is associated with a later chronotype.Carriers of a particular allele fall asleep on average 30–60 minutes later and experience greater resistance to early rising — not out of laziness, but because their biological clock runs slightly slower.
Historical context: The first 'clock' genes were discovered in the fruit flyDrosophila melanogaster in 1971 bySeymourBenzer andRonaldKonopka.They found mutants with rhythm periods of 19 hours, 29 hours, or no rhythm at all — depending on which version of the period (per) gene the fly carried.This was the first direct genetic evidence of a molecular clock.The 2017Nobel work grew directly from this discovery.
ThePER3 gene comes in two main variants byVNTR repeat length: short (4 repeats) and long (5 repeats).A study byDerk-JanDijk and colleagues at theUniversity ofSurrey (2003) found:
In 2019, a team fromMassachusettsGeneralHospital published inNatureCommunications the largestGWAS of chronotype at the time: 697,828 participants from theUKBiobank.They identified 351 genetic loci associated with morning or evening preference.These included genes affecting retinal light sensitivity, the sleep cycle, metabolism, and evenBMI.
The conclusion: chronotype is a highly polygenic trait.No single gene determines whether you are a lark or an owl.It is the result of the combined contribution of hundreds of variants — and simultaneously the interaction with age, light exposure, and routine.
—Continued inPROMaterial —
ThePRO material contains the checklist 'YourChronotype': how to determine your chronotype, how to find the keySNPs in yourDNA test, and how to adapt your daily schedule to your genetically optimal sleep rhythm.
Premium contains the longreid 'Sleep andDNA': what happens to the genome during sleep, why chronic sleep deprivation accelerates biological ageing, and which genes protect against the consequences of sleepless nights.
MAPASGEN — the podcast about genetics that is already reshaping your life.
MAPASGEN — mapasgen.com