Which enzyme is commonly used in PCR to synthesize DNA?

Which enzyme is commonly used in PCR to synthesize DNA?

• A. RNA Polymerase
• B. DNA Ligase
• C. Helicase
• D. Taq Polymerase

Answer: (D)

PCR relies on a DNA polymerase to synthesize new DNA during the extension step, starting from primers and using nucleotides to build the complementary strand. The enzyme used is thermostable, so it remains active at the high temperatures needed to separate DNA strands each cycle. This stability lets the polymerase function throughout the cycle, copying the target region efficiently. Taq polymerase, from Thermus aquaticus, is the classic example because it tolerates those heat conditions, enabling rapid, repeated extension after denaturation and annealing. Other enzymes perform different tasks and don’t synthesize DNA in this context: RNA polymerase makes RNA instead of DNA; DNA ligase seals nicks in DNA; helicase unwinds the double helix but does not add nucleotides. If higher accuracy is required, other polymerases with proofreading activity can be used, but they may be less heat-stable or slower.

PCR relies on a DNA polymerase to synthesize new DNA during the extension step, starting from primers and using nucleotides to build the complementary strand. The enzyme used is thermostable, so it remains active at the high temperatures needed to separate DNA strands each cycle. This stability lets the polymerase function throughout the cycle, copying the target region efficiently. Taq polymerase, from Thermus aquaticus, is the classic example because it tolerates those heat conditions, enabling rapid, repeated extension after denaturation and annealing.

Other enzymes perform different tasks and don’t synthesize DNA in this context: RNA polymerase makes RNA instead of DNA; DNA ligase seals nicks in DNA; helicase unwinds the double helix but does not add nucleotides. If higher accuracy is required, other polymerases with proofreading activity can be used, but they may be less heat-stable or slower.