Chromatogram from an automated DNA sequencer

    The computer scans vertically through each lane of the gel file, and converts the pattern of bands to an individual chromatogram with a series of "peaks" corresponding to each of the bands in the DNA sequence as it passes the reader. These are shown as the pseudo-colors A C G & T.  DNA migration slows over the course of the electrophoresis, and multiple bases towards the end may appear as a single broad band instead of discrete "peaks". This phenomenon is similar to the compression that occurs at the top of an autoradiograph. The data are presented in two lines: the lower the original calls of the computer, and the upper a line editable by the user. In this experiment, automatic base calling is 100% accurate to position 684 [a double-wide TT peak is corrected to a single T] and >98% accurate to the end of the DNA template at 787 bases. Manual editing produces effectively 100% accuracy.