Any of the specific endonucleases (q.v.) present in many strains of E. coli that recognize and degrade DNA from foreign sources. These nucleases are formed under the directions of genes called restriction alleles. Other genes called modification alleles determine the methylation pattern of the DNA within a cell. It is this pattern that determines whether or not the DNA is attacked by a restriction enzyme. See modification methylases, restriction endonuclease.
Subjects: Genetics and Genomics.