Restriction enzyme: one enzyme from bacteria that canrecognize certain base assignment in DNA and cut the DNA in ~ that site (the border site). A restriction enzyme acts as a biochemical scissors. Also called a limit endonuclease.A limit enzyme is a protein produced by bacteria the cleaves DNA at details sites. Bacteria usage restriction enzyme to defend versus bacterial viruses referred to as bacteriophages (or phage). When a phage infects a bacteria, that inserts that DNA right into the bacteria so the it might be replicated. The border enzyme prevents replication of the phage DNA by cut it into many pieces. Restriction enzymes were named for their capacity to restrict, or limit, the number of strains of bacteriophage that deserve to infect bacteria. Limit enzymes deserve to be isolated from bacteria and used in the activities to reduced DNA. They space indispensable devices in recombinant DNA modern technology and hereditary engineering. Every restriction enzyme recognizes a short, details sequence of nucleotide bases (the four basic chemical subunits the the direct double-stranded DNA molecule-- adenine, cytosine, thymine, and guanine). This stretches in the DNA are referred to as recognition sequences and are randomly distributed throughout the DNA. Various bacterial types make border enzymes the recognize various nucleotide sequences. ~ a restriction endonuclease recognizes a sequence, that cuts v the DNA molecule by catalyzing the hydrolysis (splitting of a chemical bond by addition of a water molecule) of the bond between adjacent nucleotides. Bacteria prevent their very own DNA from being degraded in this way by disguising their recognition sequences. Enzymes called methylases include methyl teams (--CH3) to adenine or cytosine bases within the acknowledgment sequence, i m sorry is hence modified and also protected native the endonuclease. The border enzyme and also its matching methylase constitute the restriction-modification device of a bacterial species.All restriction enzymes are different. There room three class of border enzymes, designated varieties I, II, and also III. Species I and also III enzymes are comparable in the both restriction and also methylase activities are lugged out through one huge enzyme complex, in contrast to the kind II system, in i m sorry the limit enzyme is elevation of the methylase. Type II border enzymes likewise differ from the various other two species in that they cleave DNA at details sites in ~ the acknowledgment site; the others cleave DNA randomly, sometimes hundreds of bases native the recognition sequence. Restriction enzyme were initially discovered and characterized by the molecular biologists Werner Arber, Hamilton O. Smith, and also Daniel Nathans who mutual the 1978 Nobel prize in medicine. The ability of restriction enzyme to reduced DNA at precise locations has actually permitted researcher to isolate gene-containing fragments and recombine them with other molecules of DNA. Much more than 2,500 kind II limit enzymes have actually been identified from a selection of bacter species.

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This enzymes recognize around 200 distinct sequences, which are 4 to eight bases in length.