To illustrate this system during talks, Goldman has made Lego versions of his DNA strings, using red, yellow, blue and green bricks to represent the four bases. When I clumsily drop one of the strings, it shatters on the floor, but we quickly use the neighbouring strands as templates for reassembling the broken one. We even deduce that a blue piece has rolled off under some furniture. The fail-safes work.
This side of crazy
In March 2012, Californian company Agilent Technologies created the DNA strands that Goldman and Birney had designed and shipped them back to the researchers. The sonnets, speech, paper, image and program all arrived as dry white dust specks at the bottom of several pinkie-sized tubes. Goldman, who hadn’t worked with lab experiments since he was 16, thought they were empty. “Nick said, ‘Agilent haven’t sent us anything! Are you going to have to write the email or am I?’,” says Birney.
When the team sequenced the DNA they received from Agilent, they reconstructed four of the files perfectly. But the Watson and Crick paper had two gaps of 25 letters each, where several consecutive fragments had mysteriously gone missing. After two days of staring, Goldman worked out that the missing pieces had matching ends that caused them to fold into a hairpin-shape – which the sequencer skips past without reading. Fortunately, the gaps were flanked by a recurring pattern, so he could enter the missing letters by hand. In the end, the team rebuilt all five files with 100% accuracy.
“I describe this project as being on just this side of crazy,” says Birney. “It works but isn’t commercially feasible now.” The exorbitant cost of making DNA is the biggest hold-up. For the moment, you need $220 to read each megabyte of DNA data but $12,400 to write it in the first place; however, these costs are likely to fall 100-fold within the next decade. They are also one-off investments; once data is written as DNA, it never needs to be re-written into new-fangled formats. Birney and Goldman predict that soon, DNA will be the ideal medium for storing data that you want to keep for a long time but not regularly revisit, such as wedding videos or the archives of huge science projects like the Large Hadron Collider at Cern.
Or, perhaps, all of human knowledge? Besides being universal, dense and easily copied, DNA is also incredibly stable. A recent study showed that DNA has a half-life of 521 years – that’s how long it takes for half the chemical bonds in its double helix to break. This estimate was based on DNA recovered from the 8,000-year-old leg bones of giant extinct birds called moas. But that’s nothing – these bones were preserved at 13C in New Zealand. Under gentler conditions, DNA’s shelf life last can stretch to tens of thousands of years. “For perspective, that’s all of modern human evolution,” says Birney.
At some point during their project, Goldman and Birney realised that such long-lasting information stored in DNA won’t just outlast new pieces of technology, but entire civilisations. They started thinking about a fanciful application: using DNA to apocalypse-proof human culture.
Imagine a future cataclysm that sends humanity back to the dark ages. Our population dwindles from billions to thousands. Electronic devices malfunction and digital information gets wiped. Languages die out, scientific knowledge is lost, and works of art are destroyed. But humanity bounces back. It takes 10,000 years but a new civilisation rises from the ashes and starts the process of re-discovery. The letters D, N and A would mean nothing to these descendants, but at some point, they would discover that a common molecule, shaped like a double helix, unites all living things. Using that molecule, we could provide them with an archive of all our scientific discoveries, our literature, and our immense treasure trove of cat videos.