Gene editing is a technology that precisely modifies the genome of an organism through artificial means. It enables targeted alterations of genes, achieving site-specific knockouts, knock-ins, and mutations of specific DNA sequences, ultimately downregulating or upregulating gene expression to confer new phenotypes on cells.

In the process of gene editing, site-specific modification relies on precise sequence recognition and cleavage. Taking the CRISPR/Cas9 system as an example, its guide RNA (gRNA) binds complementarily to the target sequence, guiding the Cas9 protein to cleave the DNA double strand at a specific location. This cleavage is highly precise and can occur at a specific site upstream of the PAM motif (Protospacer-adjacent motifs). Following cleavage, the cell initiates DNA damage repair mechanisms, allowing scientists to achieve site-specific modifications by providing specific repair templates or utilizing the cell's own repair capabilities.

• ZFNs, as one of the pioneering techniques in genome editing, are renowned for their exceptional precision. By integrating zinc finger DNA-binding domains with nucleases, ZFNs achieve highly specific gene modifications, delivering robust and consistent results. Their pioneering role has laid the foundation for the subsequent development of more advanced technologies like CRISPR-Cas9.

• TALENs represent a meticulously engineered class of proteins specifically designed to target and modify distinct DNA sequences with remarkable accuracy. Their structured and methodical approach minimizes off-target effects, thereby enhancing the precision and reliability of genetic modifications.

• Compared to cutting-edge technologies such as ZFNs and TALENs, the CRISPR-Cas9 system offers a precise gene editing technique. Due to its simplicity and efficiency, the CRISPR-Cas9 system has rapidly become the genome engineering tool of choice for constructing animal models, drug development, gene therapy, agricultural breeding and many other applications.