What does exonic mean?
'Exonic' is a technical adjective used in molecular biology to describe anything pertaining to exons — the segments of a gene whose sequence is retained in the mature messenger RNA after the intervening, non-coding introns have been spliced out. Because exons encode the instructions for building proteins, an exonic mutation can directly change a protein's amino acid sequence, which makes the term central to discussions of genetic disease, gene annotation, and sequencing studies. In practice it appears almost exclusively attributively, in phrases such as 'exonic sequence', 'exonic variant', or 'exonic region', and its natural counterpart is 'intronic', describing features located within introns. Though unfamiliar to most general readers, the word has become increasingly common as whole-genome and whole-exome sequencing have entered routine medicine, making it a useful term for anyone following modern genetic research.
adjectiveOf or relating to an exon, the coding segment of a gene that survives RNA splicing and contributes to the mature messenger RNA.
- Relating to or consisting of exons, the coding regions of a gene that are retained in mature messenger RNA after splicing.
"The mutation lies within an exonic region of the gene, directly altering the protein's amino acid sequence."
"Researchers identified several exonic variants associated with the disorder."
"The assay was designed to target all exonic regions across the transcriptome."
Strip away a gene's introns and what remains are its exons — so every protein your body builds is written entirely in 'exonic' code.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of exonic
'Exonic' derives from 'exon', a term coined by American molecular biologist Walter Gilbert in the late 1970s to describe gene segments that are expressed — Gilbert formed it from 'expression' plus the '-on' suffix already common in molecular biology coinages. The adjective adds the standard English adjectival ending '-ic'. Its closest relatives are the derived terms built on the same stem, notably 'exome', denoting the complete set of exons in a genome.
How exonic is actually used
'Exonic' is a technical term confined almost entirely to molecular biology and genomics literature; it rarely appears outside scientific writing. It is typically used attributively before nouns such as 'sequence', 'mutation', or 'region'. The contrasting term 'intronic' describes features of introns, the non-coding segments removed during splicing.
Easily confused with exonic
An exon is the noun denoting the coding DNA segment itself, while 'exonic' is the adjective describing anything relating to such segments.
An axon is the long fibre of a nerve cell, unrelated to genetics; 'exonic' pertains to gene sequences.