Scientists work toward storing digital information in DNA

RECORDING HISTORY:A gel image of the DNA of 96 horses displayed on a computer monitor at the UC Davis veterinary genetics lab in Davis, California.— Photo: AP  

Her computer, Karin Strauss says, contains her “digital attic” a place where she stores that published math paper she wrote in high school, and computer science schoolwork from college.

She’d like to preserve the stuff “as long as I live, at least,” says Ms. Strauss, 37. But computers must be replaced every few years, and each time she must copy the information over, “which is a little bit of a headache.”

It would be much better, she says, if she could store it in DNA the stuff our genes are made of. Ms. Strauss, who works at Microsoft Research in Redmond, Washington, is working to make that sci-fi fantasy a reality.

She and other scientists are not focused on finding ways to stow high school projects or snapshots or other things an average person might accumulate, at least for now. Rather, they aim to help companies and institutions archive huge amounts of data for decades or centuries, at a time when the world is generating digital data faster than it can store it.

Long-term repository

It helps to know how companies, governments and other institutions store data now. For long-term storage, it’s typically disks or a specialised kind of tape, wound up in cartridges about three inches on a side and less than an inch thick.

A single cartridge containing about half a mile of tape can hold the equivalent of about 46 million books of 200 pages apiece, and three times that much if the data lends itself to being compressed.

A tape cartridge can store data for about 30 years under ideal conditions, says Matt Starr, chief technology officer of Spectra Logic, which sells data-storage devices. But a more practical limit is 10 to 15 years, he says.

It’s not that the data will disappear from the tape. A bigger problem is familiar to anybody who has come across an old eight-track tape or floppy disk and realised he no longer has a machine to play it. Technology moves on, and data can’t be retrieved if the means to read it is no longer available, Mr. Starr says.

Into this world comes the notion of DNA storage. DNA is by its essence an information-storing molecule; the genes we pass from generation to generation transmit the blueprints for creating the human body. That information is stored in strings of what’s often called the four-letter DNA code. That really refers to sequences of four building blocks abbreviated as A, C, T and G found in the DNA molecule. Specific sequences give the body directions for creating particular proteins.

Digital devices, on the other hand, store information in a two-letter code that produces strings of ones and zeroes. A capital ‘A’, for example, is 01000001.

Converting digital information to DNA involves translating between the two codes. In one lab, for example, a capital A can become ATATG. The idea is once that transformation is made, strings of DNA can be custom-made to carry the new code, and hence the information that code contains.

One selling point is durability. Scientists can recover and read DNA sequences from fossils of Neanderthals and even older life forms. So as a storage medium, “it could last thousands and thousands of years,” says Luis Ceze of the University of Washington, who works with Microsoft on DNA data storage.

Compact fit

Advocates also stress that DNA crams information into very little space. Almost every cell of your body carries about six feet of it; that adds up to billions of miles in a single person. In terms of information storage, that compactness could mean storing all the publicly accessible data on the Internet in a space the size of a shoebox, Mr. Ceze says.

In fact, all the digital information in the world might be stored in DNA that fits in space the size of a large van, says Nick Goldman of the European Bioinformatics Institute in Hinxton, England.

“There’s always going to be someone in the business of making a DNA reader because of the health care applications,” Mr. Goldman says.

Getting the information into DNA takes some doing. Once scientists have converted the digital code into the 4-letter DNA code, they have to custom-make DNA. Twist Bioscience of San Francisco used a machine to create the strings letter by letter, like snapping together Lego pieces to build a tower. The machine can build up to 1.6 million strings at a time.

Each string carried just a fragment of information from a digital file, plus a chemical tag to indicate what file the information came from. — AP