DNA is a great way to store information—just ask your cells. Its molecules are stable, and billions of base pairs coil neatly into a few microns in a cell nucleus. While it’s easy for a cell to read information from DNA, a cell can’t rewrite new data into its DNA sequence.
But now synthetic biologists at Stanford have managed to pull off that very trick. To do so, they had to abandon the genetic code of ATCG and get a DNA sequence to act like bits—pieces of binary information—in a computer. The memory system uses two enzymes that can cut out and reintegrate a sequence of DNA in a live cell. Crucially, the attachment sites are designed so that the DNA sequence can be flipped every time it is put back in. The sequence oriented one way would represent 1, and its inversion is 0.
This may sound unnecessarily convoluted and maybe even a little inefficient—this DNA “bit” took three years to engineer—but synthetic biologists have something bigger brewing on their hands. By working out the pieces of a biological circuit, they hope to get cells to perform computations. A DNA bit, for example, can be used as a counter for cell divisions, perhaps as part of circuitry that shuts down a cell when division goes awry, as in cancer.
This paper published in PNAS comes from the lab of Drew Endy, an assistant professor at Stanford best known for his work with BioBricks. BioBricks are a set of standardized DNA sequences that synthetic biologists can snap together into a biological circuit—analogous to the wires, transistors, and capacitors of an electronic circuit. (To learn more, read this Wired feature about Endy and BioBricks.) Scientists have gotten RNA or DNA sequences to act like computers before, understanding Boolean logic and even doing square roots.
The principles behind biocircuitry are simple—the challenge is getting them to work in the messy, “wetware” environment of a cell. Rewritable data storage in the DNA of live cells gets it one step closer.
[via Scientific American]
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