In DNA replication, which enzyme builds (synthesizes) new DNA strands by adding nucleotides to the growing chain?

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

Answer: (A)

Verified step by step guidance

1. Understand the role of each enzyme listed in the problem: DNA polymerase, helicase, DNA ligase, and primase.
2. Recall that helicase unwinds the DNA double helix by breaking hydrogen bonds between base pairs, preparing the strands for replication.
3. Recognize that primase synthesizes a short RNA primer, which provides a starting point for DNA synthesis but does not build the DNA strand itself.
4. Know that DNA ligase joins Okazaki fragments on the lagging strand by forming phosphodiester bonds, sealing nicks in the sugar-phosphate backbone.
5. Identify that DNA polymerase is the enzyme responsible for adding nucleotides to the growing DNA strand by complementary base pairing, effectively synthesizing the new DNA strand.