What are the different types of gene editing?

There is a huge demand for successful gene-editing technology to make gene therapy the future of medicine. The possibility of curing a whole host of nasty diseases by correcting a single faulty gene is one so many scientists are working towards. There are four main gene-editing technologies to consider. Zinc Finger Nucleases (ZFNs) are artificial restriction enzymes programmed to cut out a selected portion of a DNA sequence. ZFNs edit genes very quickly. However, they can be very challenging to design and are expensive. Transcription Activator-Like Effector Nucleases (TALEN) has a TAL protein that identifies the defective gene and an endonuclease that then cuts the DNA strand so that only the functional DNA is "produced". TALENs are said to be easier and cheaper to design and program but are not best suited for targeting multiple genes. Adeno-Associated Viruses (AAV) uses a harmless vector virus to deliver functional gene copies to cells that have a defective version. Although AAV is said to have strong specificity, the vector virus is so small so it’s unsuitable for larger genes. Also, there is a possibility that the virus could be attacked by immune responses. CRISPR-Cas9 synthesizes RNA molecules that bind to the Cas9 enzyme. This enzyme cuts the DNA at targeted locations where genetic material can then be inserted or taken away. 

Resource: https://investingnews.com/daily/life-science-investing/genetics-investing/4-gene-editing-technologies-explained/