Researchers have encoded a form of rewritable memory into DNA. The arduous work involved in building the system is almost as notable as the achievement itself, says Drew Endy of Stanford University in California who led the work, which is published in Proceedings of the National Academy of Sciences. Synthetic biologists have long sought to devise biological data-storage systems because they could be useful in a variety of applications, and because data storage will be a fundamental function of the digital circuits that the field hopes to create in cells.

Rewritable biological memory circuits have been made previously, for instance from systems of transcription factors, which can be used to shut gene expression on or off in a cell. In such systems, once the memory state of the circuit is set, it can be erased and encoded with a new memory state, as is done in everyday devices such as personal computers.