share the same tag sequences derived from each of the two single parental strands (Fig. 1b). After sequencing, members of each tag family are grouped and a consensus sequence is established for each of the two strands to form ‘single-strand consensus sequences’ (SSCSs; Fig. 1c). The two complementary consensus sequences derived from the two strands of an individual DNA duplex are then compared with each other, and the base identity at each position is retained only if the two strands match perfectly at that position, yielding a ‘duplex consensus sequence’ (DCS; Fig. 1c). Mutations introduced during PCR by DNA polymerase misincorporations or arising from DNA damage will appear in only one of the two DNA strands and thus are not counted as real mutations.
