A restriction enzyme (or restriction endonuclease) is an enzyme that cuts DNA at specific recognition nucleotide sequences known as restriction sites. Restriction enzymes are commonly classified into three types, which differ in their structure and whether they cut their DNA substrate at their recognition site, or if the recognition and cleavage sites are separate from one another. To cut DNA, all restriction enzymes make two incisions, once through each sugar-phosphate backbone (i.e. each strand) of the DNA double helix.
These enzymes are found in bacteria and archaea and probably evolved to provide a defense mechanism against invading viruses. Inside a bacteria, the restriction enzymes selectively cut up foreign DNA in a process called restriction; while host DNA is protected by a modification enzyme (a methylase) that modifies the bacterial DNA and blocks cleavage. Together, these two processes form the restriction modification system.
Over 3000 restriction enzymes have been studied in detail, and more than 600 of these are available commercially. These enzymes are routinely used for DNA modification and manipulation in laboratories, and are a vital tool in molecular cloning.
Other articles related to "restriction enzyme, restriction enzymes, enzyme, restriction":
... See the main article on list of restriction enzyme cutting sites ... Examples of restriction enzymes include Enzyme Source Recognition Sequence Cut EcoRI Escherichia coli 5'GAATTC 3'CTTAAG 5'---G AATTC---3' 3'---CTTAA G---5' EcoRII ...
... A restriction fragment is a DNA fragment resulting from the cutting of a DNA strand by a restriction enzyme (restriction endonucleases), a process called restriction ... Each restriction enzyme is highly specific, recognising a particular short DNA sequence, or restriction site, and cutting both DNA strands at specific ... Most restriction sites are palindromic, (the sequence of nucleotides is the same on both strands when read in the 5' to 3' direction), and are four to eight nucleotides long ...
... Part of the probe includes the Recognition site for the restriction enzyme Dde I (underlined) ... In part 1b, the restriction enzyme has cleaved the probe and its target (Dde I leaves three bases unpaired at each end) ... The mismatched hybrid no longer acts as a recognition site for the restriction enzyme, and the probe remains at its original length ...
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