Restriction enzyme

A restriction enzyme recognizes a particular DNA sequence and cuts DNA at or near that site. In bacteria and archaea, these enzymes can help destroy invading genetic material.

Restriction–modification system: A microbial defense system in which restriction enzymes cut unprotected DNA while companion methyltransferases modify host DNA. It pairs sequence-specific cutting with chemical protection of the host genome.
Restriction mapping: A method for inferring DNA structure by comparing fragment sizes after digestion with restriction enzymes. Different cut patterns reveal the positions of recognition sites in a DNA molecule.
Werner Arber: A Swiss microbiologist whose work established the role of restriction and modification in bacterial defense. His research helped explain why bacteria restrict foreign DNA.
CRISPR-Cas9: A programmable genome-editing system that uses a guide RNA to direct Cas9 to a chosen DNA target. Unlike most restriction enzymes, it can be retargeted by changing its guide RNA.
DNA methylation: The addition of methyl groups to DNA bases, often changing how proteins recognize or regulate DNA. Host DNA methylation can mark restriction sites as protected from cleavage.
DNA cloning: The production of copies of a DNA sequence, often by inserting it into a replicating vector. Matching restriction-generated ends can join an insert to a plasmid vector.
Hamilton O. Smith: An American microbiologist who isolated and characterized the Type II restriction enzyme HindII. HindII demonstrated that an enzyme could cut DNA at specific sequences.
Meganuclease: A DNA-cutting enzyme that recognizes a long sequence, often making its natural target highly specific. Its longer recognition site contrasts with the short sites typical of many restriction enzymes.
Type II restriction enzyme: A class of restriction enzyme that typically cuts DNA at a defined position within or near its recognition sequence. These enzymes exemplify precise sequence recognition and are widely used in laboratories.
Recombinant DNA: DNA molecules assembled from genetic material originating from different sources. Restriction enzymes can cut DNA fragments that are joined to construct recombinant molecules.

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