What are Okazaki fragments?

• A. Continuous segments on the leading strand
• B. RNA primers used during priming
• C. Enzymes that unwind double helix
• D. Short DNA fragments synthesized on the lagging strand and later joined

Answer: (D)

During DNA replication, the two strands are antiparallel, so the new strand on the lagging template can’t be made continuously in the same direction as the fork. Instead, it’s built in short, discontinuous pieces known as Okazaki fragments. Each fragment starts with an RNA primer laid down by primase, and DNA polymerase extends from that primer in the 5' to 3' direction, producing a small DNA segment. After the fragments are synthesized, the RNA primers are removed and replaced with DNA, and the fragments are joined together by DNA ligase to form a continuous lagging strand. So, Okazaki fragments are the short DNA pieces on the lagging strand that are later connected.