What is the primary function of DNA ligase in genetic engineering?

The primary function of DNA ligase in genetic engineering is to bind nucleotides together by facilitating the formation of phosphodiester bonds between adjacent nucleotides on the DNA strand. This enzyme plays a critical role in the DNA replication process, as well as in processes such as DNA repair and the recombination of DNA fragments. In genetic engineering, DNA ligase is essential for combining different pieces of DNA, allowing researchers to insert genes into plasmids or other vectors, effectively creating recombinant DNA.

The other options describe different processes or functions: replicating RNA does not involve DNA ligase, as that process is primarily associated with RNA polymerase. Cutting DNA at specific sites is the task of restriction enzymes, rather than DNA ligase. Enhancing protein synthesis relates more to the function of ribosomes and various factors in transcription and translation, rather than to the role of DNA ligase.