Which process fills gaps left after RNA primers are removed during replication?

• A. Ligases alone seal the gaps.
• B. Topoisomerases fill in with nucleotides.
• C. DNA polymerases fill in the gaps with DNA and DNA ligase seals.
• D. Primers are added again.

Answer: (C)

When RNA primers are removed during replication, the gap is filled by DNA polymerases synthesizing DNA in place of the RNA. This DNA replacement creates a continuous strand, and then DNA ligase seals the remaining nick by forming the final phosphodiester bond. Ligase by itself can’t add nucleotides to fill the gap, and topoisomerases don’t insert DNA bases—they primarily relieve supercoiling. Primers are not re-added at this stage; they’re replaced by DNA and then sealed to complete the strand.