DNA sequencing reaches the space age

Space-age technology has helped US researchers develop the smallest ever DNA sequencing device, which needs just 1 femtomole of DNA.

The DNA sequencer, only 10cm in diameter, comprises a complex network of microscopic pumps, valves, heaters and electrophoresis channels, many of which were initially developed for use in a device to detect life on Mars.

The lead scientist on the project, chemist Richard Mathies at the University of California, Berkeley, has adapted the technology to carry out Sanger sequencing, the predominant method of DNA sequencing. The technique he used involves synthesising different length copies of a single DNA strand, in which the final base on each copy is labelled with one of four different fluorescent tags, and different length copies are then separated by capillary electrophoresis.

The hand-held device is able to combine these three main sequencing steps - thermal cycling (to generate the different length DNA strands); sample purification; and capillary electrophoresis - into a single automated process. The size of the device means it requires a fraction of the expensive chemical reagents normally needed for DNA sequencing, greatly reducing the running costs.

Mathies and his colleagues tested their device on 1 femtomole of a DNA strand, and found that it could calculate the sequence of the first 556 bases with 99 per cent accuracy. They are now looking at ways to increase the sensitivity and accuracy of the device still further, so that it will work with even smaller DNA samples.

’[This] represents an important milestone in the history of Sanger sequencing,’ said Michael Jones, head of the Genomics Core Laboratory at Imperial College, London. ’To just inject a template DNA, primer and terminator mix into the instrument and then sit, sipping coffee, in front of a computer screen watching the sequence appear is fantastic.’

Jon Evans