Which short fragments are produced on the lagging strand during discontinuous DNA synthesis?

Which short fragments are produced on the lagging strand during discontinuous DNA synthesis?

• A. Okazaki fragments
• B. Telomeres
• C. Promoters
• D. Exons

Answer: (A)

The short fragments produced on the lagging strand are Okazaki fragments. Because DNA polymerase can only add nucleotides in the 5' to 3' direction, the lagging strand, which runs opposite to the fork’s movement, must be synthesized in short, separately primed segments. Each fragment starts with an RNA primer laid down by primase, and DNA polymerase extends from that primer until it reaches the previous fragment. The RNA primers are later removed and the fragments joined by DNA ligase to form a continuous strand. In contrast, the leading strand is made continuously in the same direction as the fork. Telomeres are repetitive ends of linear chromosomes, promoters are transcription start sites, and exons are the coding portions of genes; these are not the short replication fragments produced on the lagging strand.

The short fragments produced on the lagging strand are Okazaki fragments. Because DNA polymerase can only add nucleotides in the 5' to 3' direction, the lagging strand, which runs opposite to the fork’s movement, must be synthesized in short, separately primed segments. Each fragment starts with an RNA primer laid down by primase, and DNA polymerase extends from that primer until it reaches the previous fragment. The RNA primers are later removed and the fragments joined by DNA ligase to form a continuous strand. In contrast, the leading strand is made continuously in the same direction as the fork. Telomeres are repetitive ends of linear chromosomes, promoters are transcription start sites, and exons are the coding portions of genes; these are not the short replication fragments produced on the lagging strand.