Which enzyme is primarily responsible for adding nucleotides to a growing DNA strand?

Which enzyme is primarily responsible for adding nucleotides to a growing DNA strand?

• A. Primase
• B. DNA ligase
• C. DNA polymerase
• D. Topoisomerase

Answer: (C)

DNA polymerase is the enzyme that adds nucleotides to a growing DNA strand. It catalyzes the formation of phosphodiester bonds as it adds each deoxynucleoside triphosphate to the 3' end of the existing strand, extending DNA in the 5' to 3' direction. A primer is needed to start this process, and that primer is laid down by primase. Once synthesis begins, polymerase continuously extends the strand, while other enzymes handle different tasks: primase provides the starting primer, ligase seals gaps between Okazaki fragments on the lagging strand, and topoisomerase relieves supercoiling ahead of the fork. Polymerase also proofreads as it goes, helping maintain fidelity.

DNA polymerase is the enzyme that adds nucleotides to a growing DNA strand. It catalyzes the formation of phosphodiester bonds as it adds each deoxynucleoside triphosphate to the 3' end of the existing strand, extending DNA in the 5' to 3' direction. A primer is needed to start this process, and that primer is laid down by primase. Once synthesis begins, polymerase continuously extends the strand, while other enzymes handle different tasks: primase provides the starting primer, ligase seals gaps between Okazaki fragments on the lagging strand, and topoisomerase relieves supercoiling ahead of the fork. Polymerase also proofreads as it goes, helping maintain fidelity.