Final answer:
DNA Polymerase is the enzyme that adds nucleotides to the growing DNA strand during replication, with DNA Polymerase III being the main enzyme for this purpose in prokaryotes.
Step-by-step explanation:
The enzyme responsible for adding nucleotides to the DNA template strands during DNA replication is DNA Polymerase. This enzyme synthesizes a new complementary DNA strand by adding nucleotides one by one against a template strand.
DNA Polymerase can only add nucleotides to the 3' end of a growing DNA chain, and this process is driven by the energy released when the bond between phosphates in nucleotide triphosphates is broken, similar to ATP. In prokaryotes, the most crucial DNA polymerase for DNA synthesis is DNA Polymerase III, whereas DNA Polymerases I and II are primarily involved in DNA repair mechanisms.