Kinetic effects of products of UV radiation DNA damage in SMRT sequencing. (a) Example sequencing trace, showing very long pausing by the polymerase upon repeated encounters with a thymine dimer (arrows) on the SMRTbell DNA template. (b) Normalized IPD ratios between the thymine dimer containing and unmodified control DNA templates. The template sequence is given as the x axis. The two template positions constituting the thymine dimer are highlighted with red bars and underlined sequence labels. The inset shows the lack of sequencing coverage after the thymine dimer position because of the extremely long pauses by the polymerase induced by the lesion.