Which enzyme catalyzes the synthesis of a new DNA strand by adding nucleotides?

Which enzyme catalyzes the synthesis of a new DNA strand by adding nucleotides?

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

Answer: (D)

During DNA replication, the enzyme that builds a new strand by adding nucleotides to the growing end is DNA polymerase. It uses the existing strand as a template and catalyzes the formation of phosphodiester bonds, adding deoxynucleoside triphosphates to the 3' end of the new strand in the 5' to 3' direction. A primer is required to start synthesis, provided by primase, after which DNA polymerase extends from that primer. Primase makes an RNA primer, helicase unwinds the double helix, and RNA polymerase (in transcription) makes RNA rather than DNA, so they don’t directly synthesize a new DNA strand. DNA polymerase is the enzyme that actually performs the DNA synthesis by incorporating nucleotides into a new DNA strand.

During DNA replication, the enzyme that builds a new strand by adding nucleotides to the growing end is DNA polymerase. It uses the existing strand as a template and catalyzes the formation of phosphodiester bonds, adding deoxynucleoside triphosphates to the 3' end of the new strand in the 5' to 3' direction. A primer is required to start synthesis, provided by primase, after which DNA polymerase extends from that primer. Primase makes an RNA primer, helicase unwinds the double helix, and RNA polymerase (in transcription) makes RNA rather than DNA, so they don’t directly synthesize a new DNA strand. DNA polymerase is the enzyme that actually performs the DNA synthesis by incorporating nucleotides into a new DNA strand.