What is the function of DNA polymerase?

• A. It synthesizes new DNA strands by adding nucleotides and also proofreads.
• B. It unzips the DNA double helix.
• C. It transcribes RNA from DNA.
• D. It degrades damaged DNA.

Answer: (A)

DNA polymerase builds new DNA strands by adding nucleotides to a growing chain using the template strand, and it also proofreads to correct mistakes. It works in the 5' to 3' direction, extending the new strand from a primer and ensuring high fidelity through a 3' to 5' exonuclease proofreading activity. This combination of synthesis and error-correction is why it’s the enzyme responsible for accurate genome replication. It doesn’t unzip the DNA double helix (that’s helicase), it doesn’t transcribe RNA from DNA (that’s RNA polymerase), and it doesn’t degrade damaged DNA (that role is filled by repair enzymes).