restriction enzyme re·stric·tion enzyme (rĭ-strĭk'shən)
Any of a group of enzymes that cleave DNA at specific sites to produce discrete fragments, used especially in gene-splicing. Also called restriction endonuclease.
Chemicals used in the lab to cut up DNA at specific sites so that it may be sequenced. They function in nature as a form of bacterial self-protection that can cut up foreign DNA. The use of restriction enzymes is crucial in DNA fingerprinting.