Alignment of reads before (a) and after (b) B-tail trimming in a selected region of the ZR reference (positions 63,633 to 63,662). Uniquely mapped reads from the Bv-95nt data set were visualized using the Tablet browser . Forward matching reads are shown in grey, reverse matching reads are shown in blue, mismatch bases are shown in white. Long white stretches are uncalled bases. Mismatches accumulated in one region, and almost all mismatches are eliminated after B-tail removal.