Extended Data Fig. 2: CRISPR array cloning method.

Schematic of CRISPR array construction. First, each fragment from an oligo pool containing multiple 3–4 spacer fragments, is amplified by limited-cycle PCR. Second, 6-spacerfragments are generated by overlap extension PCR of the 3–4-spacer fragments. Third, overlapping ends are added to the 6-spacer fragments by limited-cycle PCR. Fourth, 12-spacer fragments are generated by overlap extension PCR of the 6-spacer fragments. Fifth, the 12-spacer fragments are cloned into backbones for sequence verification. Sixth, overlapping ends are added to the 12-spacer fragments by limited cycle PCR. Seventh, 24-spacer fragments are generated by overlap extension PCR of the 12-spacer fragments by overlap extension PCR. Finally, the 24-spacer fragments are cloned into backbones for sequence verification.