What is the role of ligase in DNA replication?

What is the role of ligase in DNA replication?

• A. Ligase unwinds DNA.
• B. Ligase copies DNA.
• C. Ligase glues/links fragments together, sealing phosphodiester gaps.
• D. Ligase degrades RNA primers.

Answer: (C)

The role of ligase in DNA replication is to join fragments by forming phosphodiester bonds, sealing the breaks between fragments so the sugar-phosphate backbone becomes continuous. On the lagging strand, DNA is made in short Okazaki fragments, and after the RNA primers are removed and the gaps filled, ligase seals the nicks to complete the new strand. This step requires energy input, typically from ATP, to catalyze the bond formation. Ligase isn’t responsible for unwinding DNA (that’s helicase), copying DNA (that’s DNA polymerase), or degrading RNA primers (that’s done by RNases or exonucleases).

The role of ligase in DNA replication is to join fragments by forming phosphodiester bonds, sealing the breaks between fragments so the sugar-phosphate backbone becomes continuous. On the lagging strand, DNA is made in short Okazaki fragments, and after the RNA primers are removed and the gaps filled, ligase seals the nicks to complete the new strand. This step requires energy input, typically from ATP, to catalyze the bond formation. Ligase isn’t responsible for unwinding DNA (that’s helicase), copying DNA (that’s DNA polymerase), or degrading RNA primers (that’s done by RNases or exonucleases).