During DNA replication, the process involves the formation of two distinct strands at each replication fork: the leading strand and the lagging strand. The leading strand is synthesized continuously in the same direction as the movement of the replication fork. This continuous replication requires only a single RNA primer, which initiates the synthesis of the leading strand.
In contrast, the lagging strand is synthesized discontinuously in the opposite direction of the replication fork movement. This results in the formation of short segments known as Okazaki fragments, named after the Japanese scientist who discovered them. Each Okazaki fragment requires its own RNA primer for initiation, leading to the necessity of multiple primers for the entire lagging strand.
As the replication fork progresses, these Okazaki fragments are eventually joined together by the enzyme DNA ligase, which covalently links the fragments to form a continuous strand. The replication process is constrained by the nature of DNA polymerase, which can only synthesize DNA in the 5' to 3' direction. This limitation necessitates the discontinuous synthesis of the lagging strand.
In summary, the leading strand is characterized by continuous synthesis with a single RNA primer, while the lagging strand is synthesized in segments, requiring multiple RNA primers and subsequent joining of Okazaki fragments. Understanding these mechanisms is crucial for grasping the complexities of DNA replication and the roles of various enzymes involved in the process.