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One of the most significant discoveries which allowed the development of recombinant DNA technology was:

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Restriction endonucleases cut double stranded DNA at specific sequences and protect against viruses in bacteria. Sequences may be palindromes, a sequence which is the same when read in either direction. For example, "Able was I ere I saw Elba."

The discovery of these enzymes allowed the development of modern recombinant DNA technology.