“Junk DNA” 

The phrase “junk DNA” has haunted human genetics ever since. In 2000, when scientists of the Human Genome Project presented the first rough draft of the sequence of bases, or code letters, in human DNA, the initial results appeared to confirm that the vast majority of the sequence—perhaps 97 percent of its 3.2 billion bases—had no apparent function. The “Book of Life,” in other words, looked like a heavily padded text.

Now, in a series of papers published in September in Nature (Scientific American is part of Nature Publishing Group) and elsewhere, the ENCODE group has produced a stunning inventory of previously hidden switches, signals and sign posts embedded like runes throughout the entire length of human DNA. In the process, the ENCODE project is reinventing the vocabulary with which biologists study, discuss and understand human inheritance and disease.