restriction endonuclease /ristrik″shən en′dōno̅o̅″klē·ās/ [L, restringere + Gk, endon, within; L, nucleus, nut kernel; Fr, diastase, enzyme] , an enzyme that cleaves DNA at a specific site. Each of the many endonucleases isolated from various bacteria acts at a different site, making it possible for researchers to divide DNA molecules at selected locations. See also restriction fragment length polymorphism.
