What is the function of DNA ligase in molecular biology?

The function of DNA ligase in molecular biology is to link DNA fragments together. This enzyme plays a crucial role in the processes of DNA replication and repair by catalyzing the formation of phosphodiester bonds between adjacent nucleotides. After DNA has been replicated or repaired, there may be gaps or "nicks" in the new strand where the DNA polymerase stopped synthesizing. DNA ligase seals these gaps, ensuring the integrity and continuity of the DNA molecule.

In processes like DNA cloning, DNA ligase is utilized to join fragments of DNA that have been cut with restriction enzymes, allowing scientists to create recombinant DNA molecules. This ability to stitch together fragments is essential in various applications, including gene cloning, genetic engineering, and the repair of damaged DNA.

While unwinding DNA strands and replicating DNA are critical functions carried out by other enzymes (such as helicase and DNA polymerase, respectively), and RNA strands are repaired by different repair mechanisms, DNA ligase specifically focuses on the linkage of DNA fragments, cementing its role in molecular biology.