Summary
Enzymes that cut DNA at specific sequences, creating sticky or blunt ends for cloning.
In depth
Type II enzymes such as EcoRI recognise palindromic sequences of 4 to 8 bp (GAATTC) and cut leaving sticky ends or blunt ends. Bacteria use them to destroy phage DNA, while methylating their own. Werner Arber, Smith and Nathans got the 1978 Nobel Prize.
Names derive from the bacterial species (EcoRI from E. coli RY13). Sticky ends allow efficient joining; compatible ends from different enzymes can be ligated. Methylation protects the host DNA.
Example: fragment lengths from digestion are used in RFLP analysis.
Restriction endonucleases are bacterial enzymes that cut DNA at specific recognition sequences, usually four to eight base pairs and often palindromic. They evolved as defence against phages, while the bacterium protects its own DNA by methylation.
Some cut straight across (blunt ends); others make staggered cuts leaving single-stranded sticky ends that readily pair with matching ends. EcoRI cuts G^AATTC. Over 3,000 are known, forming the toolkit of cloning, mapping and diagnostics.
Example: cutting a plasmid and a gene with the same enzyme gives compatible ends.
Remember: DNA ligase seals the joined pieces, and the sequence of recognition site decides fragment sizes seen on a gel.
Frequently asked questions
What is Restriction Enzymes?
Enzymes that cut DNA at specific sequences, creating sticky or blunt ends for cloning.
Which area of biology covers Restriction Enzymes, and how advanced is it?
Restriction Enzymes is one of the 56 topics in Biotechnology & Genomics. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include DNA Ligase, Recombinant DNA, Gene Cloning Workflow.
Can you give an example of Restriction Enzymes?
HindIII and BamHI are common in the lab.
What should I learn before Restriction Enzymes?
Work through the Beginner topics in Biotechnology & Genomics first, such as Biotechnology, Genetic Engineering, Selective Breeding, then return to Restriction Enzymes. Intermediate topics assume the Beginner vocabulary.
What topics are related to Restriction Enzymes?
The closest topics to Restriction Enzymes are DNA Ligase, Recombinant DNA, Gene Cloning Workflow, Genetic Engineering. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Restriction Enzymes?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Restriction Enzymes. To practise the whole of Biotechnology & Genomics, use the Biotechnology & Genomics quiz.
How is Restriction Enzymes different from DNA Ligase?
Restriction Enzymes: Enzymes that cut DNA at specific sequences, creating sticky or blunt ends for cloning. DNA Ligase: The enzyme that joins DNA fragments by forming phosphodiester bonds. Read both side by side and note what each one explains.
How should I study Restriction Enzymes step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with DNA Ligase and explain the difference aloud. Finally, take the Biotechnology & Genomics quiz and come back to this page for any question you miss.