Exons

Part of speech: noun

Pronunciation: /ˈɛksɒnz/

Definitions

1. A portion of a gene that contributes to protein synthesis by containing coding sequences, which are retained in mature RNA after the removal of non-coding regions
2. A segment within a gene that encodes for proteins, playing a key role in determining the functional aspects of genetic information
3. A segment of DNA within a gene that contains instructions to produce parts of a protein and remains in the final RNA molecule after processing

Etymology: "Exons" is the plural of "exon," and the word was coined by the American biochemist Walter Gilbert in 1978 as a blend of "expressed region" and "intron," the term for the non-coding stretches it was paired with. Gilbert needed a name for the segments of a gene that are actually expressed, meaning those that end up in the finished messenger RNA, and he built it from the prefix "ex-" of "expressed" plus the second half of "intron." The pairing is deliberate. Introns are the intervening sequences that are spliced out of RNA before translation, so "exon" and "intron" name the two complementary parts of the same gene, the kept and the discarded. Gilbert's coinage gave researchers a precise vocabulary for a distinction that had only just been discovered in the late 1970s.

Synonyms: gene sequences