What is the significance of the Okazaki fragments in DNA replication?

Okazaki fragments are essential for the replication of the lagging strand during DNA replication.

Okazaki fragments are short sequences of DNA nucleotides (approximately 100 to 200 base pairs long in eukaryotes, and up to 1000 base pairs in prokaryotes) which are synthesised discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication. They were discovered in 1968 by Reiji and Tsuneko Okazaki, who the fragments are named after.

DNA replication is a complex process that involves the unwinding of the double helix structure of the DNA molecule. This unwinding is performed by an enzyme called DNA helicase. Once the DNA is unwound, another enzyme, DNA polymerase, synthesises a new strand of DNA using the original strand as a template. However, DNA polymerase can only add nucleotides in the 5' to 3' direction. This means that while one strand (the leading strand) can be synthesised continuously, the other strand (the lagging strand) must be synthesised in fragments, which are the Okazaki fragments.

The synthesis of the Okazaki fragments begins with the creation of a short RNA primer by the enzyme RNA primase. This primer serves as a starting point for DNA polymerase. The DNA polymerase then adds DNA nucleotides to the primer, creating an Okazaki fragment. Once an Okazaki fragment has been synthesised, the RNA primer is removed by another enzyme, DNA polymerase I, and replaced with DNA. The gaps between the Okazaki fragments are then sealed by DNA ligase, creating a continuous DNA strand.

The discovery and understanding of Okazaki fragments have been crucial in our understanding of the process of DNA replication. Without the formation of these fragments, the replication of the lagging strand would not be possible, and the integrity of the genetic information could be compromised. Therefore, Okazaki fragments play a vital role in maintaining the accuracy of DNA replication and, consequently, the correct transmission of genetic information from one generation to the next.