What does epigenome mean?
The epigenome is the complete collection of chemical modifications attached to an organism's DNA and its associated histone proteins — including patterns such as DNA methylation and histone acetylation — that govern how genes are expressed without changing the underlying genetic sequence. While every cell in a body contains the same genome, the epigenome varies from cell type to cell type, helping explain how one set of genes can produce neurons, muscle cells, and blood cells alike. Unlike the fixed sequence of DNA, the epigenome is dynamic: factors such as diet, stress, aging, and environmental exposures can reshape it over time, and some marks can even persist across generations. The term appears most often in genetics research, medical literature, and science reporting, typically in phrases like "map the epigenome" or "epigenome-wide association studies." Its adjective form is "epigenomic," and the related field is known as epigenetics. Understanding the epigenome is central to modern efforts to explain development, disease susceptibility, and the interplay between inheritance and environment.
nounThe complete set of chemical modifications to the DNA and histone proteins of an organism's genome that regulate gene activity without altering the underlying genetic sequence. These epigenetic marks — such as DNA methylation and histone modification — determine which genes are switched on or off in a given cell.
- Biology: the complete set of chemical compounds (such as methyl groups) attached to an organism's genome that modify gene expression without changing the DNA sequence itself.
"Environmental factors such as diet and stress can leave lasting marks on the epigenome, altering how genes are expressed."
"Scientists at the institute published the first comprehensive atlas of the human epigenome in over a hundred tissue types."
"Because identical twins share a genome but diverging epigenomes, researchers can study how lifestyle shapes long-term health."
The plural is used mainly when comparing the epigenomes of different organisms, cell types, tissues, or individuals; the singular with the definite article is more common when discussing the concept in general.
"The study compared epigenomes across dozens of tissue types to chart how gene regulation changes with age."
Your DNA is the same in every cell of your body — it's the epigenome that decides whether a cell becomes a neuron or a skin cell, and some of its marks can be passed on without changing a single letter of your genetic code.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does epigenome come from?
The word "epigenome" combines the prefix "epi-", from Greek meaning "upon," "above," or "in addition to," with "genome," itself a 20th-century blend of "gene" (from German "Gen," ultimately from Greek "genos," meaning "birth" or "origin") and "-ome," a suffix denoting a complete collection. It arose alongside the field of epigenetics, which was pioneered by British biologist Conrad Waddington in the mid-twentieth century; Waddington's term "epigenetics" drew on the older biological notion of "epigenesis." The compound gained currency in the 1990s and early 2000s as large-scale projects began systematically mapping these chemical marks across the human genome.
Related word forms
How epigenome is actually used
A technical term used primarily in genetics, molecular biology, medicine, and science journalism. It is almost always used with the definite article ("the epigenome") when referring to the concept generally. The adjective "epigenomic" describes things relating to the epigenome, as in "epigenomic data." The word is neutral in register but belongs to formal and scientific discourse; it is rarely heard in everyday conversation except in popularized discussions of health and heredity.
Easily confused with epigenome
The genome is the full set of DNA sequences an organism carries, while the epigenome is the layer of chemical tags on that DNA and its proteins that controls which genes are active.