Which enzyme is responsible for joining nucleotides to form a DNA molecule during replication?

• A. Primase
• B. Ligase
• C. Helicase
• D. DNA Polymerases

Answer: (D)

DNA polymerase is the enzyme that builds the new DNA strand by linking nucleotides together. It adds each nucleotide to the 3' end of the growing chain, using the template strand to choose the correct base, and forms the phosphodiester bonds that create the sugar-phosphate backbone. This synthesis happens in the 5' to 3' direction and requires a primer to start.

Other enzymes have different roles: primase makes the RNA primer needed to begin synthesis, helicase unwinds the double helix, and ligase seals the remaining nicks between Okazaki fragments after synthesis is finished. But the actual joining of nucleotides to form the polymerized DNA molecule is the job of DNA polymerase.