'Junk' DNA Has Evolutionary Importance

The observation that evolutionary rates for "junk" DNA (i.e. non-protein-coding DNA) are slower than anticipated suggests that there is selective pressure for sequence conservation. This in turn suggests that there is functional significance to the nucleotide sequences found within the intergenic DNA of an organism. The emerging consensus brings us back to the very old idea that much of the non-coding DNA is regulatory. Indeed, the observation that structural and functional conservation of proteins is maintained across vast evolutionary distances, suggests that differential gene regulation is key to species differences rather than differential protein function.