Restriktióendonukleázok

Restriktióendonukleázok, commonly known as restriction enzymes, are a class of enzymes that cleave DNA molecules at specific recognition nucleotide sequences, known as restriction sites. These enzymes are naturally found in bacteria and archaea, where they serve as a defense mechanism against invading foreign DNA, such as that from viruses. The bacteria protect their own DNA from cleavage by these enzymes through methylation at the restriction sites.

Restriction enzymes are categorized into three main types: Type I, Type II, and Type III, based on their subunit structure, mode of action, and cofactor requirements. Type II restriction enzymes are the most widely used in molecular biology because they recognize and cleave DNA at specific, often short, palindromic sequences, and their activity is typically independent of DNA methylation. This predictable and precise cutting action makes them invaluable tools for DNA manipulation.

In molecular biology laboratories, restriction enzymes are routinely used for various applications, including gene cloning, DNA fingerprinting, and the construction of recombinant DNA molecules. By cutting DNA at specific points, researchers can isolate genes of interest, insert them into vectors, and generate modified DNA sequences for further study or application. The fragments generated by restriction enzyme digestion can be separated by size using gel electrophoresis, facilitating analysis and manipulation. The commercial availability of a wide array of restriction enzymes with different specificities has revolutionized genetic engineering and our understanding of molecular biology.