Definition

Noun: A restriction enzyme is a type of protein that acts as molecular scissors. It recognizes a specific, short sequence of nucleotides (a restriction site) within a DNA molecule and cuts the DNA at or near that site. These enzymes are naturally produced by bacteria as a defense mechanism to cut and disable the DNA of invading viruses. In biotechnology, they are essential tools for cutting DNA at precise locations, which is a fundamental step in recombinant DNA technology, genetic engineering, and DNA analysis.

Usage

Restriction enzymes are used to manipulate DNA sequences in a controlled manner. * Scientists use a restriction enzyme to cut a gene out of a chromosome. * The DNA fragment was produced by digesting the plasmid with a restriction enzyme. * Choosing the correct restriction enzyme is crucial for ensuring the DNA pieces have compatible ends for ligation.

Advanced Usage

• Restriction Enzyme Digestion: The process of using a restriction enzyme to cut DNA into fragments.
  • The first step in cloning is often a restriction enzyme digestion of both the insert and the vector.
• Restriction Site: The specific DNA sequence recognized and cut by a given restriction enzyme.
  • The gene of interest must not contain the restriction site for the enzyme we plan to use.

Variants and Related Words

• Restriction Endonuclease: A more technical synonym for restriction enzyme, specifying it cuts within the DNA strand (endo-).
• Restriction Fragment: A piece of DNA resulting from cleavage by a restriction enzyme.
• Ligase: An enzyme that joins DNA fragments together, often used after restriction enzymes have created the fragments.

Synonyms

• Restriction endonuclease
• Molecular scissors (informal, descriptive term)

Related Phrases and Concepts

• Sticky Ends / Cohesive Ends: When a restriction enzyme cuts DNA strands unevenly, producing short, single-stranded overhangs that can easily bind to complementary sequences.
  • Enzymes like EcoRI create sticky ends, which facilitate the joining of DNA fragments.
• Blunt Ends: When a restriction enzyme cuts both DNA strands at the same point, producing fragments with no overhang.
  • SmaI is a restriction enzyme that generates blunt ends.
• DNA Ligase: The enzyme used to permanently join DNA fragments that have been cut by restriction enzymes.
  • After the restriction enzyme cut the DNA, DNA ligase was used to seal the new gene into the plasmid.

Noun

1. any of the enzymes that cut nucleic acid at specific restriction sites and produce restriction fragments; obtained from bacteria (where they cripple viral invaders); used in recombinant DNA technology