Which enzyme creates a short RNA primer to initiate DNA replication?

Which enzyme creates a short RNA primer to initiate DNA replication?

• A. RNA primase
• B. DNA ligase
• C. Hydrogen bond
• D. Base pairs

Answer: (A)

DNA replication relies on an RNA primer to begin synthesis because DNA polymerases can’t start from nothing—they need a 3′ hydroxyl end to extend. The enzyme that creates this short RNA primer is RNA primase, a small RNA polymerase that lays down a brief stretch of RNA. On the leading strand, one primer suffices to start continuous synthesis; on the lagging strand, primase repeatedly adds primers for each Okazaki fragment, which are then extended by DNA polymerase. After synthesis, the primers are removed and replaced with DNA, and DNA ligase seals the gaps between fragments. The other options don’t perform primer creation: DNA ligase seals nicks after primer removal, hydrogen bonds are interactions between bases, and base pairs describe which bases pair with which, not an enzyme.

DNA replication relies on an RNA primer to begin synthesis because DNA polymerases can’t start from nothing—they need a 3′ hydroxyl end to extend. The enzyme that creates this short RNA primer is RNA primase, a small RNA polymerase that lays down a brief stretch of RNA. On the leading strand, one primer suffices to start continuous synthesis; on the lagging strand, primase repeatedly adds primers for each Okazaki fragment, which are then extended by DNA polymerase. After synthesis, the primers are removed and replaced with DNA, and DNA ligase seals the gaps between fragments. The other options don’t perform primer creation: DNA ligase seals nicks after primer removal, hydrogen bonds are interactions between bases, and base pairs describe which bases pair with which, not an enzyme.