Summary
The enzyme that joins DNA fragments by forming phosphodiester bonds.
In depth
T4 DNA ligase seals nicks by making phosphodiester bonds using ATP; works on sticky and blunt ends. In cells, it joins Okazaki fragments and repairs DNA.
Ligase needs a 5' phosphate and 3' hydroxyl. Sticky ends anneal first by base pairing, then ligase seals the backbone. Alkaline phosphatase prevents vector self-ligation.
Common mistake: ligase joins DNA backbones but does not itself find matching sequences.
DNA ligase catalyses the formation of a phosphodiester bond between a 3' hydroxyl and a 5' phosphate, sealing nicks in the sugar-phosphate backbone, using ATP or NAD+ as energy source.
In cells it joins Okazaki fragments during lagging strand replication and repairs breaks. In the lab, T4 DNA ligase joins sticky or blunt ends of fragments cut by restriction enzymes, producing recombinant molecules; reaction temperature and the ratio of insert to vector matter.
Example: ligating a gene into a plasmid cut with the same enzyme.
Common mistake: confusing ligase with polymerase; ligase seals existing nicks, while polymerase adds new nucleotides.
Frequently asked questions
What is DNA Ligase?
The enzyme that joins DNA fragments by forming phosphodiester bonds.
Which area of biology covers DNA Ligase, and how advanced is it?
DNA Ligase 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 Gene Cloning Workflow, Restriction Enzymes, Recombinant DNA.
Can you give an example of DNA Ligase?
Ligation reactions in cloning use a vector to insert ratio of about 1:3.
What should I learn before DNA Ligase?
Work through the Beginner topics in Biotechnology & Genomics first, such as Biotechnology, Genetic Engineering, Selective Breeding, then return to DNA Ligase. Intermediate topics assume the Beginner vocabulary.
What topics are related to DNA Ligase?
The closest topics to DNA Ligase are Gene Cloning Workflow, Restriction Enzymes, Recombinant DNA, Plasmid Vectors. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand DNA Ligase?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for DNA Ligase. To practise the whole of Biotechnology & Genomics, use the Biotechnology & Genomics quiz.
How is DNA Ligase different from Gene Cloning Workflow?
DNA Ligase: The enzyme that joins DNA fragments by forming phosphodiester bonds. Gene Cloning Workflow: Cut the gene and vector, ligate, transform bacteria, select colonies and screen for the insert. Read both side by side and note what each one explains.
What is a common mistake about DNA Ligase?
Ligase joins DNA backbones but does not itself find matching sequences.
How should I study DNA Ligase 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 Gene Cloning Workflow and explain the difference aloud. Finally, take the Biotechnology & Genomics quiz and come back to this page for any question you miss.