A segment of a gene that contains information used in coding for protein synthesis. Genetic information within genes is discontinuous, split among the exons that encode for messenger RNA and absent from the DNA sequences in between, which are called introns. Genetic splicing, catalyzed by enzymes, results in the final version of messenger RNA, which contains only genetic information from the exons. Compare intron.
Stretches of DNA in genes that code for proteins. In eukaryotes, exons in a given gene are generally separated from each other by stretches of DNA that do not contain instructions for constructing proteins. (Compareintron.)