"Junk" DNA similar in mouse, rat and human genomes.
"Only a tiny fraction of [DNA] actually makes up what are conventionally thought of as genes little stretches of DNA that make protein," says David Haussler, director of the Center for Biomolecular Science and Engineering at the University of California at Santa Cruz. "Probably the fraction of the DNA that actually is genes in the traditional sense of making proteins is as little as 1.2 percent. The rest of the DNA is what people used to call "junk."
All DNA gets passed down from parent to offspring, a process that's been going on for billions of years. "About four to five hundred million years ago, the common ancestor of fish, birds and mammals was a creature that lived in the ocean," explains Haussler, "and that creature passed on DNA to its offspring and they passed on the DNA to their offspring, and through the millions of years different species have evolved from a common ancestor."
When Haussler and his colleague Gill Bejerano used computers to compare the human genome with the mouse and the rat genomes, they assumed that because humans, mice, and rats look so different, there would be differences in the genome. They did see the expected differences in the shared genes from the common ancestor, but they were surprised to find long stretches of shared "junk" DNA that were exactly the same in humans and rodents.<hl> "There were about five hundred stretches of DNA in the human genome that hadn't changed at all in the millions and millions of years that separated the human from the mouse and the rat</hl>," says Haussler. "I about fell off my chair. It's very unusual to have such an amount of conservation continually over such a long stretch of DNA."
This research appeared in the <http://www.sciencemag.org/cgi/content/abstract/sci;317/5840/915?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=Haussler&andorexacttitle=or&titleabstract=Junk+DNA&andorexacttitleabs=or&andorexactfulltext=or&searchid=1&FIRSTINDEX=0&sortspec=relevance&fdate=7/1/2003&tdate=4/30/2009&resourcetype=HWCIT,HWELTRAugust, 2007 online version of Science </a> and was funded by the National Human Genome Research Institute, the National Cancer Institute, the National Institutes of Health, and the Howard Hughes Medical Institute.