Which enzyme is responsible for assembling nucleotides to create DNA?

The enzyme responsible for assembling nucleotides to create DNA is DNA polymerase. This enzyme plays a critical role during DNA replication by adding complementary nucleotides to the growing DNA strand, ensuring that the new strand is synthesized in the 5' to 3' direction.

DNA polymerase has several key functions, including the ability to proofread and correct mistakes during DNA synthesis, which is essential for maintaining the integrity of the genetic information being copied. It catalyzes the formation of phosphodiester bonds between the nucleotides, effectively linking them into a continuous DNA strand.

In the context of the other enzymes mentioned, DNA ligase is involved in joining OKasaki fragments during the replication of the lagging strand, but it does not synthesize nucleotides. RNA polymerase is responsible for synthesizing RNA from a DNA template during transcription, while helicase unwinds the DNA double helix, preparing the strands for replication but not directly participating in the assembly of nucleotides. Thus, DNA polymerase is the key enzyme for building DNA.