How does the synthesis of the leading strand differ from that of the lagging strand during DNA replication in bacteria?
The synthesis of the leading strand is continuous, moving toward the replication fork, while the lagging strand is synthesized discontinuously in short segments called Okazaki fragments, moving away from the replication fork.
During DNA replication in bacteria, the leading strand is synthesized continuously in the 5' to 3' direction towards the replication fork. This is because the DNA polymerase III can add nucleotides in this direction as it follows the opening of the replication fork. In contrast, the lagging strand is oriented in the 3' to 5' direction relative to the replication fork, which necessitates a different approach. It is synthesized discontinuously in short segments known as Okazaki fragments. These fragments are later joined together by DNA ligase after the RNA primers are replaced with DNA by DNA polymerase I. This process allows both strands to be synthesized simultaneously despite their opposite orientations.
Key points
- Leading strand synthesis is continuous and moves toward the replication fork.
- Lagging strand synthesis is discontinuous, forming Okazaki fragments.
- DNA polymerase III synthesizes DNA in the 5' to 3' direction.
- RNA primers are used to initiate synthesis on the lagging strand.
- Okazaki fragments are joined by DNA ligase after primer removal.
- DNA polymerase I replaces RNA primers with DNA on the lagging strand.
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Talaro's Foundations in Microbiology
Kathleen Park Talaro
EIGHTH EDITION · McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc.