Ligase

Definition

Ligase is an enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. It plays a crucial role in DNA replication and repair.

5 Must Know Facts For Your Next Test

1. 1. Ligase is essential for sealing nicks in the sugar-phosphate backbone of DNA during replication.
2. 2. It specifically acts on the lagging strand to join Okazaki fragments into a continuous strand.
3. 3. ATP or NAD+ are commonly used cofactors for ligase activity, providing the necessary energy for bond formation.
4. 4. In prokaryotes, DNA ligase I is primarily responsible for joining the fragments.
5. 5. Mutations or deficiencies in ligase can lead to errors in DNA replication, potentially resulting in genetic disorders.

Review Questions

• 1. What role does ligase play in DNA replication?
• 2. Which specific fragments does ligase join on the lagging strand?
• 3. What energy source does ligase use to catalyze the formation of phosphodiester bonds?

Related terms

Helicase: An enzyme that unwinds the DNA double helix ahead of the replication fork

Okazaki Fragments: Short sequences of DNA nucleotides which are synthesized discontinuously and later linked by ligase

DNA Polymerase III: The primary enzyme responsible for DNA synthesis during replication