What are fragments produced by DNA polymerase on the lagging strand?

• A. Okazaki fragments
• B. Replication bubbles
• C. Primer fragments
• D. Telomeres

Answer: (A)

On the lagging strand, DNA polymerase makes DNA in short bursts because synthesis must proceed 5' to 3' even as the fork opens. The template runs 3' to 5' in the direction away from the fork, so a continuous chain isn’t possible. Primase lays down RNA primers at intervals, and DNA polymerase extends from each primer to create short DNA pieces. Those pieces are called Okazaki fragments. Later, another enzyme, DNA ligase, joins the fragments to form a continuous strand. The other terms don’t describe these transcription-like pieces produced during lagging-strand synthesis—replication bubbles are early regions where strands separate, primer fragments isn’t a standard term, and telomeres are the chromosome ends.