Fig. 4.

a Cel-I assay (Surveyor nuclease assay) scheme: PCR products of wild-type DNA and mutated DNA of the ZFN-targeted locus are hybridized, allowing individual DNA strands to reassort. Incubation with the Surveyor nuclease cleaves the resulting base mismatches or loops. b The digestion products are electrophoresed; cleavage products are only seen when wild-type and mutant DNA are mixed (50 % PCR product, 25 % cleavage product each). When performed on ZFN-modified samples, the diversity of alleles generated by NHEJ allows the Cel-I assay to report the degree of gene modification