SHARED SCRIPT. “An organism’s DNA thus is not only a “book” about the organism, but is also a book about the environment it lives in, including the species it co-evolves with. It is well known that not all of the symbols in an organism’s DNA correspond to something. These sections, sometimes referred to as “junk-DNA,” usually consist of portions of the code that are unexpressed or untranslated (i.e., excised from the mRNA).”
http://www.pnas.org/content/97/9/4463.full