système de restriction-modification

CONT: Il existe chez la plupart des bactéries un système dit de ""restriction-modification"" codé par le chromosome bactérien, des plasmides, ou même certains bactériophages.

CONT: Investigation has shown that this restriction was due to bacterial enzymes that recognize specific sites on a ""foreign"" viral DNA and cleave that DNA. To protect its own DNA the bacterial cell makes a modification enzyme that adds methyl groups to nucleotides constituting the recognition sites for the restriction endonuclease, making them resistant to cleavage (modification-restriction system).