What are Okazaki fragments?

Okazaki fragments are crucial components in DNA replication, particularly in the synthesis of the lagging strand. During DNA replication, the double helix unwinds, and each strand serves as a template for creating a new complementary strand. DNA polymerase can only add nucleotides in the 5' to 3' direction, which presents a challenge for the lagging strand; because it runs in the opposite direction relative to the replication fork, it cannot be synthesized continuously.

Instead, the lagging strand is synthesized in small, discontinuous sections known as Okazaki fragments. These fragments are synthesized in a series of short runs, often ranging from 100 to 200 nucleotides in eukaryotes. Each fragment is initiated by an RNA primer and extended by DNA polymerase until it reaches the next fragment. After all fragments are synthesized, they are joined together by DNA ligase to form a continuous strand. This process ensures that both strands of the DNA helix are replicated accurately and efficiently.

Understanding Okazaki fragments provides insight into the complex mechanisms of DNA replication and underscores the distinct roles played by different strands during this fundamental biological process.