Restriction enzymes, also known as restriction endonucleases, are enzymes that recognize specific DNA sequences and cleave the DNA at or near those recognition sites. They are called "molecular scissors" because they have the ability to cut DNA molecules at specific points.
Restriction enzymes are produced by bacteria as a defense mechanism against invading viral DNA. These enzymes recognize and bind to specific DNA sequences, called restriction sites, and then cleave the DNA at those sites. The resulting DNA fragments can be used in various molecular biology techniques such as DNA cloning, gene mapping, and genetic engineering.
The discovery and application of restriction enzymes have revolutionized molecular biology and have been instrumental in many areas of genetic research. They allow scientists to manipulate and analyze DNA molecules with precision, making them essential tools in molecular biology laboratories.