Before answering this question, what on earth is X-Large DNA? This news release from Stanford University says that scientists there have created a molecule of DNA wider than the ones found in living creatures in our world.
Scientists at Stanford University have created an expanded molecule of DNA with a double helix wider than any found in nature. Besides being more heat resistant than natural DNA, the new version glows in the dark -- a property that could prove useful in detecting genetic defects in humans.
Before going further, here are some basic explanations about DNA.
DNA typically comes in the form of a double helix --s two parallel strands of genetic information coiled together like a long, twisted ladder. Each rung of the ladder consists of two complementary units, called "bases," that bind together in "base pairs."
Only four bases exist in nature: adenine (A), thymine (T), guanine (G) and cytosine (C). Because of their unique size and shape, T always pairs with A, and G with C. Any other combination (such as AC or GT) would be too wide or too narrow to fit inside the double helix.
In their study, Eric Kool, a professor of chemistry at Stanford, and his group, followed experiments from the 1970s when chemist Nelson Leonard created an expanded base -- xA -- that was about one-third wider than normal A.
The Stanford group used a similar technique to create xT -- a synthetic base that's twice as big as natural T.
Success came when they paired an expanded A with a normal T (xAT) and an expanded T with a normal A (xTA). Using this arrangement, the researchers were able to synthesize a double helix that could stretch just enough to hold the expanded base pairs intact. The result was a stable new form of DNA that's about 20 percent wider than natural DNA. The researchers named the new molecule "expanded DNA," or xDNA.
Besides being more stable, the xDNA is fluorescent. Now, we can answer the question: what to do with x-large DNA?
This fluorescent property could prove useful for medical biopsies, Kool said, adding: "You need fast and accurate ways of genetically typing cells, and I think color is an interesting way of doing that. You'd put a thin slice of tissue on a slide, stain it with your molecule, look at it under a microscope and say, 'Ah! This tumor has this mutation in its DNA, so now we know what drugs to use to treat it.'"
If you prefer a *funnier* answer to this more serious one, you can read "DNA, Now in XXX-Large," which tells you that xDNA is the key to find life on other planets.
Perhaps the sexiest aspect of XDNA is that it could be the genetic material for a form of life that has already populated other planets, according to Kool. The researchers don't know yet that XDNA can replicate, but Kool hopes to find out.
"Life on other planets has to have something that codes information and can transfer it," Kool said, "but who's to say it has to be the exact structure of DNA we have? Who's to say that our kind of DNA is better and more viable?"
Sources: Mark Shwartz, Stanford University, October 24, 2003; Kristen Philipkoski, Wired News, October 30, 2003
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