RNA primers have what role in replication?

• A. They terminate replication
• B. They provide a starting point for DNA polymerase to begin synthesis
• C. They are the final part of the DNA strand
• D. They are templates for RNA transcription

Answer: (B)

DNA polymerase can only add nucleotides to an existing 3' end, so replication needs a starting point. RNA primers provide that starting point by being a short RNA sequence laid down by primase. Once the primer is in place, DNA polymerase can extend the new DNA strand from its 3' end. On the leading strand, one primer is enough to start continuous synthesis; on the lagging strand, multiple primers set up short segments called Okazaki fragments that are later joined together. Primers aren’t signals to terminate replication, they aren’t the final part of the DNA, and they aren’t templates for RNA transcription. After synthesis, the RNA primers are removed and replaced with DNA.