Restriction enzyme

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Restriction enzyme

An enzyme, specifically an endode-oxyribonuclease, that recognizes a short specific sequence within a deoxyribonucleic acid (DNA) molecule and then catalyzes double-strand cleavage of that molecule. Restriction enzymes have been found only in bacteria, where they serve to protect the bacterium from the deleterious effects of foreign DNA. See Deoxyribonucleic acid (DNA)

There are three known types of restriction enzymes. Type I enzymes recognize a specific sequence on DNA, but cleave the DNA chain at random locations with respect to this sequence. They have an absolute requirement for the cofactors adenosine triphosphate (ATP) and S-adenosylmethionine. Because of the random nature of the cleavage, the products are a heterogeneous array of DNA fragments. Type II enzymes also recognize a specific nucleotide sequence but differ from the type I enzymes in that they do not require cofactors and they cleave specifically within or close to the recognition sequence, thus generating a specific set of fragments. It is this exquisite specificity which has made these enzymes of great importance in DNA research, especially in the production of recombinant DNAs. Type III enzymes have properties intermediate between those of the type I and type II enzymes. They recognize a specific sequence and cleave specifically a short distance away from the recognition sequence. They have an absolute requirement for the ATP cofactor, but they do not hydrolyze it.

A key feature of the fragments produced by restriction enzymes is that when mixed in the presence of the enzyme DNA ligase, the fragments can be rejoined. Should the new fragment carry genetic information that can be interpreted by the bacterial cell containing the recombinant molecule, then the information will be expressed as a protein and the bacterial cell will serve as an ideal source from which to obtain that protein. For instance, if the DNA fragment carries the genetic information encoding the hormone insulin, the bacterial cell carrying that fragment will produce insulin. By using this method, the human gene for insulin has been cloned into bacterial cells and used for the commercial production of human insulin. The potential impact of this technology forms the basis of the genetic engineering industry. See Enzyme, Genetic engineering

References in periodicals archive ?
BseDI represent one of the restriction enzymes of type II which is able to recognize the nucleotide sequence and cut the DNA molecule specifically.
Similarly, the restriction enzymes NlaIV and BsaJI were suitable for discriminating the Indian mud crab species when using the other COI gene fragment (597-bp PCR amplicon produced by the second set of primers).
Restriction enzymes and expected fragment sizes Restriction Expected DNA SNP Enzyme fragments M680I Hinf I Wild; 126 bp+234 bp Mutant; 360 bp M694V Hph I Wild; 195 bp+23 bp Mutant; 218 bp M694I Pag I Wild; 195 bp Mutant; 182 bp+13 bp V726A Alu I Wild; 360 bp Mutant; 320 bp+40 bp SNP: single-nucleotide polymorphism; bp: base pair Table 2.
We propose a new shape of transition molecules and another kind of restriction enzymes, which cut only when the ligation of a transition molecule to the circular molecule of the input will be accomplished on both sides.
Restriction enzymes can slow or halt this absorption process.
2C of 100x BSA, 5 [micro]l of template and 1 [micro]l of restriction enzyme.
Follow this by explaining that restriction enzymes recognize a certain sequence (or pattern) of DNA nucleotides (Figure 3).
At this stage, the plasmid DNA was digestable by most restriction enzymes for a quick DNA analysis.
The amplified products of msp-2, csp and ama-1 genes were digested with Hinf-1, Ssp-1 and Dra-1 restriction enzymes respectively.
For TRFLP analysis, PCR amplicons are fluorescently tagged at the 5' end and cut with restriction enzymes, and the terminal restriction fragments can then be quantified by electrophoresis to yield an index of microbial composition, relative abundance, and overall diversity (Blackwood et al.
The 13 strains selected from MLST groupings were run with PFGE using the restriction enzymes AscI and ApaI.

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