Restriction endonucleases, often referred to as restriction enzymes, are specialized proteins that act as molecular scissors capable of cutting DNA at specific sequences. These enzymes are naturally found in bacteria and archaea, where they serve as a defense mechanism against invading viral DNA, particularly bacteriophages. They recognize particular short DNA sequences, usually 4 to 8 base pairs long, known as recognition sites, and cleave the DNA at or near these sites. The specificity of this cleavage allows researchers to manipulate DNA precisely in the laboratory, making restriction endonucleases a cornerstone of recombinant DNA technology. Restriction enzymes are classified into several types based on their structure, recognition site, and cleavage pattern. Type I enzymes cut DNA at random sites far from the recognition sequence and require ATP and S-adenosyl methionine for activity, making them less commonly used in molecular biology. Type II restriction enzymes, the most widely used, cleave DNA at specific recognition sites, usually palindromic sequences,