New restriction sites can be generated by ligation of DNA fragments with compatible ends. These ends may be generated by:

1. Cleavage followed by fill-in of 5´ overhangs to generate blunt ends.
2. Cleavage with two restriction endonucleases that produce blunt ends.
3. Cleavage with two restriction endonucleases that produce compatible overhangs.

Compatible ends, generated by each of the above methods, can be ligated to produce DNA sequences that often contain useful restriction endonuclease sites. Generation of these sites is detailed in the following tables.

Restriction endonucleases that produce compatible cohesive ends often produce recleavable ligation products. The combinations listed were identified by computer analysis, and although we have tried to ensure their accuracy, they have not necessarily been confirmed by experimentation.

Where isoschizomers exist, only one member of each set is listed. Only enzymes available from New England Biolabs have been listed.

Enzymes that have degenerate recognition sequences (i.e. recognize more than one sequence) are followed by a specific sequence in parentheses and are only listed if a non-degenerate equivalent does not exist. Be aware that these degenerate enzymes will cleave sequences in addition to the one listed.

A "--" denotes a ligation product that cannot be recleaved.

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