Definition

Noun: A type of enzyme (nuclease) that cuts (cleaves) the phosphodiester bonds within the interior of a nucleic acid chain (DNA or RNA). This action produces fragments of varying lengths, in contrast to an exonuclease, which removes nucleotides from the ends of the chain.

Usage

Endonucleases are fundamental tools in molecular biology and genetics. * Restriction endonucleases are used to cut DNA at specific sequences, enabling gene cloning and analysis. * Researchers used an endonuclease to digest the genomic DNA into smaller fragments for sequencing. * The activity of a specific endonuclease can produce a characteristic pattern of DNA fragments.

Advanced Usage

• Restriction Endonuclease: A specific class of endonucleases that recognize and cut DNA at or near specific, short nucleotide sequences (recognition sites). They are critical for recombinant DNA technology.
  • EcoRI is a well-known restriction endonuclease that cuts DNA at the sequence GAATTC.
• DNA Repair Endonucleases: Enzymes involved in cellular DNA repair pathways that make internal cuts to remove damaged sections of DNA.
  • The AP endonuclease initiates repair by cutting the DNA backbone at a site lacking a base.

Variants and Related Words

• Endonucleolytic (adjective): Relating to or characterized by the action of an endonuclease.
  • The endonucleolytic cleavage was confirmed by gel electrophoresis.
• Exonuclease (noun): A related nuclease that removes nucleotides from the free ends of a nucleic acid chain, rather than from the interior.

Synonyms

• Restriction enzyme (specifically for restriction endonucleases)
• DNA cutter (informal, general)

Related Phrases/Concepts

• Cleavage site: The specific bond or sequence where the endonuclease cuts.
• Sticky ends / Blunt ends: The types of DNA fragment ends produced by different endonucleases after cutting.
• Gel electrophoresis: The common technique used to visualize the DNA fragments produced by endonuclease digestion.

Noun

1. a nuclease that cleaves nucleic acids at interior bonds and so produces fragments of various sizes