Biomedicine How the Heliscope Sequences DNA Helicos Biosciences’ novel machine could speed up sequencing and unearth new disease-linked genetic variations. by Emily Singer June 23, 2008 Sponsored by Each “flow cell” has 25 channels, each capable of holding 16 million strands of DNA for sequencing. A coating on the surface of the cell allows it to be washed clean between reactions. To start the sequencing process, a scientist uses a multitip pipette to inject DNA samples into the flow cell. The flow cell is then loaded into the HeliScope, which contains a complex optical system and four digital cameras. A granite slab, seen as a horizontal stripe across the top of the photo, prevents the instrument from vibrating. DNA bases–A, C, T, and G–and DNA polymerase, the enzyme that catalyzes the sequencing reaction, are fed to the flow cell through a complex fluidics system at precisely timed intervals. A low-power laser illuminates the sequencing reactions, which are recorded by the digital cameras. The data recorded by the cameras is transferred to an accompanying processing center, which converts the images into strings of DNA letters. A specialized algorithm assembles the overlapping fragments into a longer sequence of DNA.