Restriktsioonienüümide

Restriktsioonienüümide, often referred to as restriction enzymes, are proteins that bind to specific DNA sequences and cut the DNA at those sites. These enzymes are crucial tools in molecular biology and are naturally found in bacteria and archaea, where they function as a defense mechanism against invading viruses. By recognizing and cleaving foreign DNA, restriction enzymes protect the host cell from infection.

The specificity of restriction enzymes is remarkable. Each enzyme recognizes a particular DNA sequence, typically 4 to 8 base pairs long, known as a restriction site. Once the restriction site is encountered, the enzyme cleaves the DNA backbone, usually creating either "sticky ends" (short, single-stranded overhangs) or "blunt ends" (where both strands are cut at the same position). The type of end created depends on the specific enzyme.

Scientists have isolated and characterized hundreds of different restriction enzymes, each with its unique recognition sequence and cleavage pattern. These enzymes are widely used in various molecular biology techniques. For instance, they are essential for gene cloning, allowing scientists to cut and insert DNA fragments into plasmids. They are also used in DNA fingerprinting, genetic engineering, and the analysis of DNA structure. The ability to precisely cut DNA at specific locations has revolutionized our understanding and manipulation of genetic material.