In vitro cutting of DNA in specific locations on the DNA.
Restriction digests are mediated by restriction enzymes, a.k.a., restriction endonucleases. Depending upon intentions, the digests can be performed either on DNA for which sequence is already known, and therefore for which restriction sites have already been identified, or instead on relatively uncharacterized DNA for which locations of restriction sites are relatively unknown.
Restriction digests are often an early gene cloning step, that is, as a means of preparing relatively small restriction fragments for the sake of insertion into a cloning vector. Restriction digests also are a means of characterizing DNA, as most notably seen with restriction fragment length polymorphism or RFLP assays.
The actual process of doing restriction digests, as is generally true with DNA manipulation in the laboratory, involves both isolation of DNA and then cleaning it, that is, separating DNA from impurities and particularly impurities that can interfere with restriction enzyme functioning and/or which can lead to DNA degradation.
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