(A) Schematic of Zwitch. (B) Schematic of the zebrafish shha locus and TALEN used to induce DNA DSBs in intron 1. Exons are indicated by filled boxes with numbers. The binding sites for the TALEN pair are highlighted in blue, and the XbaI site in the spacer region is highlighted in green. (C) The efficiency of the TALENs in introducing DSBs. XbaI digestion of PCR products amplified from the genomic DNA of embryos injected with TALEN mRNAs. The efficiency of the TALEN pair in inducing DSBs (67%) was quantified from the gel image using ImageJ software. (D) Schematic of the strategy used to target shha via TALEN-mediated homologous recombination with pZwitch-shha-int1. (E) The screening process for founders. (F) Genomic PCR analysis of the Zwitch insertion with the correct orientation. (G) Southern blot analysis of the Zwitch-modified shha allele. BGHpA, bovine growth hormone polyadenylation signal; cryaa, α A-crystallin; LA, left arm; RA, right arm.