Epigenomic

Part of speech: adjective

Definitions

1. Relating to the epigenome or to epigenomics, the study of chemical modifications that switch genes on or off without altering the underlying DNA sequence
2. Describing the study or features of the full set of epigenetic marks across a genome that influence how genes are expressed without changing their sequence
3. Concerning the layer of heritable regulatory changes, such as DNA methylation and histone modification, that shape gene activity across an organism's entire genome

Etymology: "Epigenomic" is a modern scientific coinage, built from "epigenome" with the adjectival suffix "-ic." The base "epigenome" combines "epi-," from the Ancient Greek preposition ἐπί ("epí," meaning "on," "upon," or "over"), with "genome," the word for an organism's complete set of genetic material. So the literal sense is something like "over the genome," and the term refers to chemical marks and other features that sit on top of the DNA sequence without altering the sequence itself. The suffix "-ic" has a long pedigree. It descends from Latin "-icus," which entered English through Old French "-ique" and Middle English "-ik," and it is the standard way English forms adjectives from nouns, as in "genomic" from "genome." Epigenomic therefore sits in a family of scientific adjectives that use the same ending. Because the word is a recent technical formation built from classical parts, it has no ancient users. Its use belongs to the period when researchers needed a precise name for the gene-regulating layer beyond the DNA sequence, and the adjective was simply the natural form of the noun "epigenome" when describing that work.