value using a physical model of the cell and its contents. The PGM base-caller takes these flow-values and corrects for phase and signal loss, and also normalizes the raw flow-values to the key sequence (the key is a known four-base DNA molecule appended to the 5′ region of every read sequence). Finally, quality assurance procedures are applied to the data, filtering polyclonal and noisy reads, and clipping adapters and low quality regions from the 3′ end of the remaining reads.
