An exon is any region of DNA within a gene that is transcribed to the final messenger RNA (mRNA) molecule, rather than being spliced out from the transcribed RNA molecule. Exons of many eukaryotic genes interleave with segments of non-coding DNA (introns). The term exon was coined by American biochemist Walter Gilbert in 1978: Function In many genes, each exon contains part of the open reading frame (ORF) that codes for a specific portion of the complete protein. However, the term exon