During DNA replication, the lagging strand is synthesized in a fragmented way. It is synthesized using the leading chain as a template.
The correct answer and explanation is:
The statement is correct. During DNA replication, the lagging strand is indeed synthesized in a fragmented manner.
DNA replication occurs in two directions due to the antiparallel nature of the two strands of the DNA molecule. The leading strand is synthesized continuously, moving in the direction of the replication fork. This is because the enzyme DNA polymerase can add nucleotides in the 5’ to 3’ direction, which is the same direction as the unwinding of the DNA helix.
On the other hand, the lagging strand is synthesized in the opposite direction. The replication fork opens up from the 5’ to 3’ direction, but the lagging strand’s template runs in the 3’ to 5’ direction. Since DNA polymerase can only synthesize DNA in the 5’ to 3’ direction, it cannot continuously add nucleotides to the lagging strand. Therefore, the lagging strand is synthesized in short fragments called Okazaki fragments.
These fragments are initially made by DNA polymerase III, which adds nucleotides in the 5’ to 3’ direction. Once a fragment is completed, another enzyme called DNA polymerase I removes the RNA primer used to initiate synthesis and replaces it with DNA. Finally, the enzyme DNA ligase joins the Okazaki fragments together by forming phosphodiester bonds between them, ensuring the lagging strand is continuously synthesized.
This fragmented synthesis occurs because of the physical constraints on the direction of replication, with the lagging strand needing to be synthesized in segments that are later connected. The overall process ensures that both strands of the DNA are replicated simultaneously and accurately.