So as we said, we have loads and loads of DNA, only some of which is protein-coding genes. For a long time, scientists thought that anything noncoding was -- it's almost rude to say it -- "junk," and labeled as such.
But now so-called junk DNA is having its day, courtesy of the Encyclopedia of DNA Elements, or ENCODE, project. Thanks to ENCODE, a group of more than 400 geneticists from around the world have been scrutinizing this DNA. Although the DNA doesn't include instructions for proteins, it wasn't just hanging around. In fact, it seems this noncoding DNA (a much kinder label) actually contained gene switches that control our genes.
To take our switch analogy further, let's think about a radio. Without some sort of switch mechanism, it wouldn't serve much good. But with an on/off mechanism -- not to mention a tuner and a volume dial -- we can make that radio work. Same with genes. A gene has to be told what to do; on its own it's just blinking 12:00, like that radio in your house. But with the switches that exist in our noncoding DNA, the genes can become activated. The gene switches determine what genes are used (and how) in a cell. Much as our radio tuner tells us if we're going to listen to pop music or NPR, our gene switches tell our genes what they're to become -- and, like turning the volume up or down, the switches determine how much protein is made and when. So our former junk DNA actually contains crucial instructions for how our genes operate within each cell.
Even more interesting is the implication that genetic switches are playing a large role in disease. Some diseases -- certain cancers, for instance -- are thought to come from changes in DNA. But ENCODE showed a link between malfunctioning genes and variants in the switches -- not a variant in the gene itself. In other words, it might not be the radio that's defective; the volume might just be broken. Which, I think we can all agree, is pretty much the coolest thing we've learned today.
Author's Note: Is the DNA between genes really junk?
It only took me one neurobiologist to relearn everything I forgot about DNA after my freshman year of high school. But it turns out that I'm not the only one who's still figuring out DNA: Researchers recently found that it was that former ne'er-do-well junk DNA (and not any particular gene itself) that contained mutations that might lead to the development of melanomas.
- Hall, Stephen S. "Hidden Treasures in Junk DNA." Scientific American. Sept. 18, 2012. (Jan. 23, 2013) http://www.scientificamerican.com/article.cfm?id=hidden-treasures-in-junk-dna
- Hamzelou, Jessica. "Global project reveals just how active our "junk" DNA is." NewScientist. Sept. 6, 2012. (Jan. 23, 2013) http://www.newscientist.com/blogs/shortsharpscience/2012/09/global-project-reveals-what-ou.html
- Harmon, Katherine. "'Junk' DNA holds clues to common diseases." Scientific American. Sept. 5, 2012. (Jan. 23, 2013) http://www.scientificamerican.com/article.cfm?id=junk-dna-encode
- Jha, Alok. "Breakthrough study overturns theory of 'junk DNA' in genome." The Guardian. Sept. 5, 2012. (Jan. 24, 2013) http://www.guardian.co.uk/science/2012/sep/05/genes-genome-junk-dna-encode
- Kolata, Gina. "Bits of mystery DNA, far from 'junk,' play crucial role." The New York Times. Sept. 5, 2012. (Jan. 23, 2013) http://www.scientificamerican.com/article.cfm?id=hidden-treasures-in-junk-dna
- Marder, Jenny. "Mysterious Noncoding DNA." PBS NewsHour. Nov. 7, 2011. (Jan. 23, 2013) http://www.pbs.org/newshour/rundown/2011/11/junk-dna.html
- McSpadden, Brian. "What's the difference between genes and DNA?" Michigan State Science Theatre. June 2, 1993. (Jan. 23, 2013) http://www.pa.msu.edu/sciencet/ask_st/060293.html
- National Institute of General Medical Sciences. "The New Genetics." National Institute of Health. June 9, 2011. (Jan. 23, 2013) http://publications.nigms.nih.gov/thenewgenetics/chapter1.html
- The New York Times. "Rethinking 'Junk' DNA (Graphic)." The New York Times. Sept. 5, 2012. (Jan. 23, 2013) http://www.nytimes.com/interactive/2012/09/06/science/rethinking-junk-dna.html
- Soden, Marta. Neurobiologist. Personal correspondence. Jan. 24, 2013.
- Walsh, Fergus. "Detailed map of genome function." BBC News. Sept. 5, 2012. (Jan. 23, 2013) http://www.bbc.co.uk/news/health-19202141
- Winstead, Edward R. "A Conversation with Dr. John Stamatoyannopoulos about ENCODE and Cancer Research." National Cancer Institute Bulletin. Sept. 18, 2012. (Jan. 23, 2013) http://www.cancer.gov/ncicancerbulletin/091812/page5