What term describes a short RNA segment used to initiate DNA synthesis?

• A. DNA Primer
• B. RNA Primer
• C. Primer RNA
• D. Initial Primer

Answer: (B)

In DNA replication, a short RNA segment is laid down to start synthesis because DNA polymerases can only add nucleotides to an existing 3' end. This RNA fragment, made by primase, provides that starting point and a free 3' hydroxyl for DNA polymerase to extend from. That’s why the term used is RNA primer. After the new DNA strand is built, the RNA primer is removed and replaced with DNA, with the remaining backbone sealed by ligase. Other phrasings like DNA primer or initial primer aren’t standard terms for this initiating segment.