A new DNA-based memory chip

25 May 2012
Posted by Sarah Castor-Perry.

Researchers have developed a DNA-based memory chip for storing information inside cells.

It could be used to record data in a living cell, without using silicon chips like we do in computers. This could allow us to track cell divisions to study cell processes like development, ageing and the changes that occur in cancer.

DNA is directional, and now a team, led by Jerome Bonnet at Stanford University have found a way to encode information using enzymes that can flip small pieces of DNA between their normal direction, which acts as a 0, and the opposite direction, which acts like a 1. This means it can store one bit of data. And the process used is reliable enough to write and rewrite information again and again.computer_chip

The researchers found that by using an enzyme called integrase, borrowed from a type of virus called a bacteriophage that attacks bacteria, they were able to chop out a small section of DNA, flip it over and stitch it back into the main DNA strand, changing its direction and therefore 'setting' the switch to 1 rather than 0.

Then by applying integrase again, this time along with another enzyme called excisionase, they were able to cut the DNA section out, flip it back to its original orientation, and stitch it back in again, 'resetting' it to 0.

It's then possible to read the data from the memory chip using different coloured proteins. When the DNA is in the 0 configuration, the green fluorescent protein or GFP gene is switched on, which makes the cell glow green. And when it's in the 1 configuration, RFP (red fluorescent protein) is produced, making the cell glow red.

This could be used to show when a cell had undergone a particular number of cell divisions, or if a particular gene had been switched on.

The enzymes used are both members of a group called recombinases, and the team have dubbed their data storage system the recombinase addressable data module, or RAD for short.

It's taken the group 3 years and 750 tries of combinations to get the RAD module right. One area where they had trouble was in finding the right balance between integrase and excisionase expression, to stop the DNA from being flipped between the two states without regulation. Eventually, they were able to engineer controllers for the 'reset' switch, to keep the flipping of the DNA regulated.

The next step for this way of storing data is not to work out how to increase the power up to a terabyte to find a new type of computer, but to get up to around 8 bits, or a byte. Drew Endy, one of the team working on this RAD system believes that the real power of it is that it can be used where silicon can't - inside living cells.

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