Restriction Endonuclease: Enzyme that can cleave DNA at a specific base-pair sequence of nucleotides.

Restriction Endonuclease: Enzyme that can cleave DNA at a specific base-pair sequence of nucleotides.

1. Cleaving

   • Sticky Ends: Short single-stranded overhang ends from cleavage. Ready to be paired with new DNA strands.
     • Restriction Enzyme cuts specific DNA sequence and is added to another DNA gene in a plasmid. The plasmid can then be injected into a bacterial cell and reproduce more genes, known as “recombinant DNA.”
   • Blunt Ends: Fully based paired ends from cleavage. Not ready to bind with new DNA strands.

2. Types

   • Type I: Cuts random sequences
   • Type II: Cuts specific areas close to or within recognition sequence - most commonly used
   • Type IIS: Cleaves outside recognition sequence to one side. Used on DNA with multiple recognition sites.
   • Type IIG: Cleaves outside recognition sequence and can switch between cleaving other DNA and protecting (methylase) own DNA
   • Type III: Cleaves outside recognition sequence and can switch between cleaving other DNA and protecting (methylase) own DNA
   • Type IV: Recognizes and cleaves modified DNA

3. Applications

   • Genetic Engineering: Molecular Biologists target sequences then isolate and cleave them. The cleaved strand is then used to modify something else
   • Restriction Fragment Lenth Polymophism (RFLP): Molecular biologists study the fragment length differences in individuals or groups of individuals
   • DNA fingerprinting
   • Immune Systems: When bacteriophage (virus) injects DNA into bacterial cell, the restriction enzyme breaks foreign DNA into segments and renders it useless.

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