What are the different types of gene editing?

Scientists have adopted 4 main types of gene editing so far:

(1) Restriction Enzymes. Restriction enzymes cleave DNA into fragments at or near specific recognition sites within molecules, presenting an opportunity to insert new DNA material at that location.

(2) Zinc Finger Nucleases (ZFNs). ZFNs are artificial restriction enzymes generated by fusing a zinc finger DNA-binding domain to a DNA-cleavage domain. Zinc finger domains can be engineered to target specific desired DNA sequences and this enables zinc-finger nucleases to target unique sequences within complex genomes.

(3) Transcription activator-like effector nucleases (TALENs). TALENs are restriction enzymes that can be engineered to cut specific sequences of DNA. They are made by fusing a TAL effector DNA-binding domain to a DNA cleavage domain (a nuclease which cuts DNA strands). Transcription activator-like effectors (TALEs) can be engineered to bind to practically any desired DNA sequence, so when combined with a nuclease, DNA can be cut at specific locations (Boch J, 2011 ).

(4) CRISPR-Cas9 Gene Editing. Clustered regularly interspaced short palindromic repeats (CRISPR) is a two-component system consisting of a guide RNA and a Cas9 nuclease. The Cas9 nuclease cuts the DNA within the ~20 nucleotide region defined by the guide RNA. With CRISPR, scientists can customize their guide RNAs, and algorithms have been developed to assess chances of off-target effects.