Zinc finger nucleases can be thought of as highly specific genome scissors. In other words they allow us to cut a genome at a chosen place. A zinc finger nuclease consists of a designed zinc finger protein or ZFP fused to the cleavage domain of the Fok1 restriction enzyme.

ZFN-mediated targeted genome editing works in four main steps:
1. ZFN pair is delivered into the cell by transfection or electroporation (nonviral methods for getting the ZFN into the cell)
2. The zinc finger protein part recognizes the target site
3. The Fok1 part gets busy chopping, creating a double strand break and the broken part dissociates away from the DNA
4. Then two things can happen depending on the design:
a. Either no repair template has been included and then the gene gets deleted in 1-20% of cases OR
b. A repair template has been included and then foreign gene can be inserted instead in 1-20% of cases!

In addition to zinc finger nucleases, two additional often used gene techniques exist. These are TALEN and CRSPR-Cas9.

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