Restriction Endonucleases: Basics and Applications

Restriction endonucleases (REs) are crucial molecular tools that have transformed genetic engineering by enabling precise DNA manipulation. They recognize and cut specific DNA sequences, laying the foundation for modern molecular biology techniques. This chapter explores the classification, structure, mechanisms, and functions of various RE types (types I–IV), emphasizing their substrate specificity, cofactor needs, and modes of cleavage. It also covers the history and naming of REs, their organization within restriction–modification (R/M) systems, and regulatory processes involving methylases and control proteins. The diverse applications of REs, including cloning, DNA fingerprinting, genome mapping, and recombinant DNA technology, are thoroughly reviewed. Special focus is placed on their vital role in creating gene libraries and advancing the development of site-specific genome editing tools like zinc-finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats-Cas9. These newer systems, which stem from basic RE principles, show how simple bacterial defense mechanisms have led to powerful, programmable genome editing platforms. In summary, restriction endonucleases remain essential in biotechnology, highlighting the significant impact of fundamental research in microbiology and enzymology.