Question

DNA replication requires which of the following enzymes?

• A. DNA polymerase only
• B. DNA polymerase and ligase
• C. Ligase only
• D. RNA polymerase

Answer 1

Answer: (B)

DNA polymerase and ligase

DNA replication requires DNA polymerase and ligase. A molecule of a DNA polymerase binds to one strand of the DNA and begins moving along it in the 3' to 5' direction, using it as a template for assembling a leading strand of nucleotides and reforming a double helix. Because DNA synthesis can only occur 5' to 3', a molecule of a second type of DNA polymerase binds to the other template strand as the double helix opens. This molecule must synthesize discontinuous segments of polynucleotides (called as Okazaki fragments). Another enzyme, DNA ligase then stitches these together into the lagging strand.