DNA No Longer Human?

From Wired.com
“Biologists Create Cells With 6 DNA Letters, Instead of Just 4”

One of the first things you learn in Biology 101 is that the genetic code consists of four letters: A, T, C, and G. Each represents a chemical building block of DNA, the molecule that encodes the information necessary to build life as we know it. But what if we didn’t have to settle for just four letters? Now, scientists have accomplished something once thought impossible: They’ve created cells with an expanded genetic alphabet that includes two more letters.

“We now have a cell that survives and lives with more information in its genome,” said Floyd Romesberg, the synthetic biologist at the Scripps Research Institute in La Jolla, California who led the work.

Having more letters to work with potentially opens the door to a huge range of novel molecules. (A rough analogy: Just think how many crazy new words you could spell with 39 letters instead of the usual 26). With further refinements, synthetic cells might one day be used to create–or evolve–proteins that don’t exist in nature, as well as new sequences of DNA and RNA, any of which could be useful for research, diagnosing disease, or creating new therapies. But that’s still a ways off.

Romesberg says his lab spent 15 years developing DNA with two extra letters. In chemical terms, the letters are nucleotides, the components of DNA whose sequences spell out instructions for making proteins. Cells, you may remember, make proteins by transcribing DNA into RNA and using the RNA as a template to string together amino acids into proteins. Cells also have to copy their DNA each time they divide to make more cells. The biggest challenge, Romesberg says, was making sure the two new nucleotides played nice with the enzymes that do all this copying and transcribing.

In 2012, the scientists reported a breakthrough: They showed that six-letter DNA they’d created could be successfully copied and transcribed into RNA in test tube experiments. It should also be possible to trick synthetic cells into evolving proteins or other molecules that are optimized for various biological tasks, Romesberg says. He has started a company, Synthorx, to explore these possibilities.

“The public is always asking, are you going to create a monster that’s going to escape and take over the world,” he said. Benner thinks those fears are overblown.