TABLE 3.

Comparison between ZFN, TALEN, CRISPR-Cas, base editors, and prime editors.

ZFN	TALEN	CRISPR-Cas	Base editors	Prime editors
Protein-based genome editing tool comprising DNA cleavage domains fok1 and synthetic zinc finger-based DNA-binding domain	Nuclease-dependent genetic engineering tool that contains the nuclease domain of the fok1 enzyme and TALE protein having customizable DNA-binding repeats	RNA-based genome editing method comprising crRNA, trans-activating CRISPR RNA (tracr RNA), and cas9 enzyme	Newly developed genome engineering tool, classified into C-to-G base editors (CGBEs), cytosine base editors (CBEs), and adenine base editors (ABE), all of which have different compositions	RNA-dependent genome engineering method comprising nCas9 (H840A) and the Moloney murine leukemia virus reverse transcriptase (M-MLV-RT)
Endonuclease
fok1	fok1	Cas9	DCas	pegRNA
NA	NA	Cas protein: Cas9	Cas protein: nCas9 (D10A)	Cas protein: nCas9(H840A)
NA	NA	RNA: single guide RNA (sgRNA)	RNA: sgRNA	RNA: prime editing guide RNA (PegRNA)
NA	NA	Reverse transcriptase: No	Reverse transcriptase: No	Reverse transcriptase: Yes
Mutation types
Gene disruption and insertions	Gene disruption and insertions	All types of base insertions, deletions, and substitutions	Transition mutations (no insertion and deletions)	All types of base insertions, deletions, and substitutions
			(CBE) for C:G to T:A transition
			(ABE) for A:T to G:C transition
			(CGBEs) for inducing transversion of C:G into G:C
Origin
Artificial gene editing technique	Artificial gene editing technique	Naturally occurring RNA-based bacterial defense mechanism	Engineered nucleases	Engineered nucleases
Mutation rate
Moderate	Moderate	Low	High	Very high
Target recognition efficiency
High	High	High	Very high	Very high
Off-target effects
High	Low	Variable	Very low	Very low