Restriction endonuclease

Definition

An enzyme that recognizes and cleaves double-stranded DNA at or near specific nucleotide sequences called restriction sites, producing fragments with predictable ends. These enzymes function as molecular scissors in DNA manipulation, enabling precise cutting of genetic material for analysis, cloning, or modification. Restriction endonucleases are classified into Types I–V based on cofactor requirements, subunit composition, and whether cleavage occurs at or distant from the recognition sequence. Type II enzymes, which cut within or immediately adjacent to their palindromic recognition sites, are most widely used in research applications.

Etymology

From Latin restrictio (limitation, confinement) and endonuclease (enzyme that cleaves internal phosphodiester bonds in nucleic acid chains); coined to describe enzymes that restrict viral DNA replication in bacteria by destroying foreign DNA at specific sites.

Example

In DNA barcoding studies of cryptic ant species, researchers use the restriction endonuclease MspI to digest cytochrome c oxidase I (COI) gene amplicons; differential cleavage patterns reveal species-specific haplotypes without full sequencing, enabling rapid identification of morphologically similar workers in mixed field collections.

Synonyms

• restriction enzyme
• REase
• restrictase

Related Terms

• DNA barcoding
• endonuclease
• polymerase chain reaction
• restriction site
• restriction fragment length polymorphism
• molecular marker
• Genetic marker

Usage Notes

The term is often shortened to 'restriction enzyme' in laboratory practice, though 'restriction endonuclease' emphasizes membership in the broader endonuclease enzyme class. Distinguish from general endonucleases, which lack sequence specificity. In arthropod molecular systematics, Type II restriction endonucleases are preferred for techniques like AFLP (amplified fragment length polymorphism) and RADseq (restriction-site associated DNA sequencing) due to their predictable cleavage patterns. Some enzymes produce blunt ends; others generate 5' or 3' overhangs ('sticky ends') that facilitate ligation into cloning vectors—an important consideration when designing genetic transformation protocols for insects such as Drosophila or CRISPR-based genome editing in mosquitoes.