Restriction enzymes.
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   A  bacterial  restriction  enzyme is an endonuclease that recognizes a
   specific DNA sequence (restriction site).
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   Many  restriction  sites are palindromes: the nucleotide sequences are
   the same in the two antiparallel strands.
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   The  endonuclease  makes  cuts  in  the  restriction  site that leaves
   staggered single-stranded ends.
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   continue