Intervening sequences exhibit distinct vocabulary.

Little is known about the origin and function of eukaryotic introns. Application of a novel linguistic approach to the analysis of intervening sequences reveals, however, that they exhibit a specific non-random vocabulary whose major feature is the utilization of mirror-symmetrical words ("mirrorrim"). Introns also manifest a significant tendency to avoid local complementarities. Possible biological implications of the corresponding loop regions in the RNA transcripts are discussed.