Which enzyme synthesizes a short RNA primer using the template DNA?

• A. DNA Polymerase
• B. Helicase
• C. Primase
• D. Ligase

Answer: (C)

Primer synthesis is needed to start DNA replication because DNA polymerase cannot initiate a new strand on its own; it can only extend an existing 3' end. The enzyme that lays down a short RNA primer using the DNA template is primase. It creates a brief RNA sequence complementary to the template, giving DNA polymerase a starting point to add DNA nucleotides and build the new strand. On the leading strand, one primer can suffice for continuous synthesis, while on the lagging strand multiple primers are laid down for the synthesis of Okazaki fragments. The other enzymes have different roles: helicase unwinds the DNA, and ligase seals remaining nicks after primers are removed and replaced with DNA. DNA polymerase, while essential for synthesis, cannot initiate from scratch and relies on the primer provided by primase.