Cloning and Mapping
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  • Restriction Enzyme Digestion

    Restriction enzymes, first described in 1971, are bacterially derived enzymes that cleave DNA. Evolutionarily, restriction enzymes arose as a bacterial self-defense mechanism; the genomes of invading organisms would be degraded, leading to an inability to replicate. Type II restriction enzymes generally recognize an inverted repeat palindrome. This recognition site structure leads to a symmetrical cleavage of both DNA strands and results in either blunt- or sticky-ends of the digested DNA. Blunt ends are universally compatible with other blunt-ended DNA and possess a 5’ phosphate group to promote ligation. Sticky ends, on the other hand, are stretches of single-stranded DNA that is capable of self-ligation or ligation with a complementary region of DNA from another molecule or organism.

    1. Type II Restriction Enzymes

      Type II restriction enzymes are most commonly used for molecular biology applications, as they recognize stereotypical sequences and produce a predictable cleavage pattern. Learn more about how Type II REs work.

    2. Type I Restriction Enzymes

      Type I restriction enzymes are a group of endonucleases that recognize a bipartite sequence, but do not produce a predictable cleavage pattern. Learn more about how Type I REs work.

    3. Type III Restriction Enzymes

      Type III restriction enzymes are a group of endonucleases that recognize a non-pallindromic sequence, comprising two inversely oriented sites. Learn more about these poorly understood enzymes.

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    Protocols for Restriction Enzyme Digestion