Table 2. Characteristics of genome editing technologies.

	ZFNs	TALENs	CRISPR/Cas9
Length of recognized DNA target	9–18bp	30–40bp	22bp + PAM sequence
DNA recognition	Multimeric protein-DNA interaction	Protein-DNA interaction	RNA-DNA interaction
Nuclease design	Difficult	Feasible	Easy
Cost	High	Moderate	Low
Success rate of nuclease design	Low	High	High
Potential off-target effects	Yes	Yes	Yes
Specificity	Moderate	High	Moderate
Sensitivity to DNA methylation	Not known	Sensitive to CpG methylation	Not sensitive to CpG methylation

CRISPR/Cas9: clustered regularly interspaced short palindromic repeats/CRISPR-associated proteins 9, PAM: protospacer adjacent motif, TALENs: transcription activator-like effector nucleases, ZFNs: zinc finger nucleases