Restriction enzymes, also known as restriction endonucleases, are proteins that act as molecular scissors, cutting DNA at specific sequences called restriction sites. These enzymes are naturally produced by bacteria as a defense mechanism against invading viruses (bacteriophages) by recognizing and cutting foreign DNA while leaving their own DNA unharmed, usually through methylation. Each restriction enzyme has a specific recognition sequence, typically 4 to 8 base pairs long, which it scans for in the DNA molecule.
