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In molecular biology, endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain (namely DNA or RNA).Some, such as deoxyribonuclease I, cut DNA relatively nonspecifically (with regard to sequence), while many, typically called restriction endonucleases or restriction enzymes, cleave only at very specific nucleotide sequences.
More than 3,600 restriction endonucleases are known which represent over 250 different specificities. [7] Over 3,000 of these have been studied in detail, and more than 800 of these are available commercially. [8] These enzymes are routinely used for DNA modification in laboratories, and they are a vital tool in molecular cloning. [9] [10] [11]
The concept is used in molecular biology, in cloning, or when subcloning insert DNA into vector DNA. Such ends may be generated by restriction enzymes that break the molecule's phosphodiester backbone at specific locations, which themselves belong to a larger class of enzymes called exonucleases and endonucleases. A restriction enzyme that cuts ...
Depiction of the restriction enzyme (endonuclease) HindIII cleaving a double-stranded DNA molecule at a valid restriction site (5'–A|AGCTT–3').. In biochemistry, a nuclease (also archaically known as nucleodepolymerase or polynucleotidase) is an enzyme capable of cleaving the phosphodiester bonds that link nucleotides together to form nucleic acids.
The restriction modification system (RM system) is found in bacteria and archaea, and provides a defense against foreign DNA, such as that borne by bacteriophages.. Bacteria have restriction enzymes, also called restriction endonucleases, which cleave double-stranded DNA at specific points into fragments, which are then degraded further by other endonucleases.
The homing endonucleases are a collection of endonucleases encoded either as freestanding genes within introns, as fusions with host proteins, or as self-splicing inteins. They catalyze the hydrolysis of genomic DNA within the cells that synthesize them, but do so at very few, or even singular, locations.
Southern invented Southern blot after combining three innovations. The first one is the restriction endonucleases, which were developed at Johns Hopkins University by Tom Kelly and Hamilton Smith. Those restriction endonucleases are used to cut the DNA at a specific sequence. Kenneth and Noreen Murray introduced this technique as Southern.
A nicking enzyme (or nicking endonuclease) is an enzyme that cuts only one strand of a double-stranded DNA or RNA molecule [1] at a specific recognition nucleotide sequence known as the restriction site.