Which enzyme is responsible for linking DNA nucleotides together during replication?

During DNA replication, the primary enzyme responsible for linking nucleotides together is DNA polymerase. This enzyme synthesizes a new DNA strand by adding nucleotides one by one to the growing strand based on the template strand.

DNA polymerase functions by catalyzing the formation of phosphodiester bonds between the nucleotides, thus creating a continuous DNA strand. It requires a primer, which is typically provided by primase, to initiate the synthesis process, but the actual linking of the nucleotides is the critical role of polymerase.

Other enzymes mentioned serve different functions: helicase unwinds the DNA double helix to allow replication, ligase is involved in joining Okazaki fragments on the lagging strand after polymerase has synthesized them, and primase synthesizes short RNA primers to provide the starting point for DNA polymerase. Therefore, the unique ability of DNA polymerase to directly build the new strand by connecting nucleotides makes it the correct answer in the context of DNA replication.