Restriction enzyme
Molecular Biology · Biotechnology · Microbiology
Say it: rih-STRIK-shun EN-zime
A restriction enzyme is a bacterial protein that cuts DNA at a specific short sequence, making it a basic tool for cutting and joining DNA.
Also: restriction endonuclease, restriction enzymes
Definition
What is a restriction enzyme?
Restriction enzymes, also called restriction endonucleases, recognize a particular short sequence of bases in double-stranded DNA, typically four to eight base pairs long, and cut the DNA at or near that site. Bacteria make them as a defense against viruses: the enzymes chop up invading phage DNA and so restrict the virus's growth, which gave them their name. A bacterium protects its own DNA by methylating the same sequences, so its enzymes leave them alone.
Thousands are known, each named after the microbe it came from; EcoRI, from E. coli, cuts the sequence GAATTC. Many recognition sites are palindromes, reading the same on both strands in the 5' to 3' direction. Some enzymes cut straight across and leave blunt ends, while others make staggered cuts that leave short single-stranded overhangs, or sticky ends, which can pair with any DNA cut by the same enzyme.
Because the cuts are predictable and work on DNA from any organism, these enzymes made recombinant DNA possible: scientists cut a plasmid and a gene with the same enzyme, then join them with DNA ligase. They are also used to map DNA and check clones.
Word parts
Where does the term “restriction enzyme” come from?
- en-
- inGreek en
- -zyme
- leaven, yeastGreek zyme
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Related
Terms that go with it
- Recombinant DNARecombinant DNA is DNA made in the laboratory by joining pieces of DNA from different sources, often different species, into one molecule.
- PlasmidA plasmid is a small, usually circular DNA molecule that copies itself independently of the main chromosome, found mostly in bacteria.
- Molecular cloningMolecular cloning is a set of laboratory methods for inserting a specific DNA fragment into a vector and copying it many times inside host cells.
- BacteriophageA bacteriophage, or phage, is a virus that infects bacteria, injecting its genome and using the host cell's machinery to make new phages.
- DNA methylationDNA methylation is the addition of a small methyl group to DNA, usually on cytosine, which can switch a gene off without changing its sequence.
- Genetic engineeringGenetic engineering is the direct change of an organism's DNA using laboratory techniques, to add, remove or alter genes and give it new traits.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- NHGRI Talking Glossary: Restriction Enzyme
- OpenStax Biology 2e, 17.1 Biotechnology
- NCBI MeSH: DNA Restriction Enzymes
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