What Is Epigenetics? How Your Life Talks to Your Genes
Every cell in your body carries the same DNA, yet a neuron and a liver cell behave completely differently. Epigenetics is a big part of the reason — and it keeps responding to how you live.
KEY POINTS
- Epigenetics is the layer of chemical marks that controls which genes are active, without changing the DNA sequence itself.
- The best-studied mark is DNA methylation, which can be measured from a blood sample.
- Epigenetic marks change with age and respond to factors such as smoking, diet, physical activity and stress.
- Unlike your DNA sequence, many epigenetic marks are dynamic, which is why they are useful for tracking health over time.
The genome is the script. Epigenetics decides which lines are read.
Your genome — the roughly three billion letters of DNA you inherit from your parents — is almost identical in every cell of your body. What differs from one cell type to another is which of your roughly 20,000 genes are switched on, switched off, or turned up and down.
Epigenetics (from the Greek epi, “on top of”) describes the chemical marks and structures that sit on top of the DNA and help control that activity. They do not change the sequence of letters. Instead, they change how accessible a gene is to the cell’s machinery, and therefore how likely it is to be used.
These marks are copied when a cell divides, which is how a skin cell keeps producing skin cells. That makes them a kind of cellular memory.
The main epigenetic marks
DNA methylation. A small chemical group (a methyl group) is attached to the DNA, mostly where the letter C is followed by a G — a so-called CpG site. Methylation near the start of a gene is generally associated with that gene being switched off. The human genome contains around 28 million CpG sites.
Histone modifications. DNA is wrapped around proteins called histones. Chemical tags on these proteins loosen or tighten the packaging, making genes easier or harder to read.
Chromatin structure and non-coding RNAs. The overall folding of DNA, and RNA molecules that do not code for proteins, add further layers of regulation.
Of these, DNA methylation is the most widely measured in research and testing, because it is chemically stable, can be read at hundreds of thousands of sites at once, and can be obtained from an ordinary blood sample.
What changes your epigenome?
Age. Methylation at many sites changes in predictable ways as we get older. This is the basis of the “epigenetic clocks” used to estimate biological age.
Lifestyle and exposures. Large population studies have found clear methylation signatures of smoking, and associations with diet, alcohol, body weight, physical activity, stress and air pollution.
Life history. A classic study of identical twins found that they are epigenetically very similar early in life, but that their epigenomes drift apart with age — especially when they live different lives.
Because many of these marks are dynamic, epigenetics offers something your DNA sequence cannot: a way to see how your biology is responding to your life now, and to measure change over time.
What epigenetics can — and cannot — tell you
An epigenetic profile reflects patterns that are statistically linked with age, exposures and disease risk in large groups of people. For an individual, it is a useful signal to discuss with a healthcare professional and to track over time. It is not, on its own, a diagnosis.
Some popular claims run ahead of the evidence. Epigenetic marks are passed on when cells divide; whether lifestyle-induced marks are passed from parents to children across generations in humans is still being debated by researchers.
Evidence at a glance
ESTABLISHED SCIENCE
- Epigenetic marks regulate gene activity without changing the DNA sequence.
- DNA methylation changes with age in predictable ways.
- Smoking leaves strong, well-replicated methylation signatures.
EMERGING RESEARCH
- How much, and how quickly, lifestyle changes can shift epigenetic measures in an individual.
- Inheritance of lifestyle-induced epigenetic marks across generations in humans.
HOW EPIX AI USES IT
- We read DNA methylation at around 930,000 CpG sites from a blood sample, and combine it with whole genome sequencing.
- Your report estimates biological age and shows which risks look more epigenetically active — an estimate to discuss with a professional, not a diagnosis.
References
- Bird A. Perceptions of epigenetics. Nature. 2007;447:396–398.
- Allis CD, Jenuwein T. The molecular hallmarks of epigenetic control. Nature Reviews Genetics. 2016;17:487–500.
- Fraga MF, et al. Epigenetic differences arise during the lifetime of monozygotic twins. PNAS. 2005;102:10604–10609.
- Joehanes R, et al. Epigenetic signatures of cigarette smoking. Circulation: Cardiovascular Genetics. 2016;9:436–447.
- López-Otín C, et al. Hallmarks of aging: an expanding universe. Cell. 2023;186:243–278.
See your own genetics and epigenetics
One blood sample: whole genome sequencing, DNA methylation analysis and an estimate of your biological age.
This article is for education and is not medical advice. An estimated biological age is not a clinical diagnosis; please discuss any health decisions with a qualified professional. Prof. Milena Georgieva is Epix AI’s co-founder and Chief Science Officer; videos are credited to their original publishers.