Okazaki fragments

Okazaki fragments can be described as those fragments of DNA which are temporary components of lagging DNA combinations at the replication fork. Thus, it can be said that Okazaki fragments are comparatively petite fragments of DNA that are synthesised on the lagging strand at the time of DNA replication. 

Okazaki Fragments

Reiji Okazaki, Tsuneko Okazaki, along with their colleagues initially discovered the Okazaki fragments whilst they were studying the duplication of bacteriophage DNA in Escherichia coli in 1968. Thus, Okazaki fragments are named after its discoverers Reiji Okazaki and his spouse, Tsuneko Okazaki.

Formation of Okazaki Fragments

During the initial phase of DNA replication, the DNA winds down and the two components of DNA split in two leading to the formation of two prongs that bear a resemblance to a fork. Therefore, this is known as the replication fork. The leading strand is the one that goes from 5’ to 3′ whereas the lagging strand is the one that goes from 3′ to 5′. Contrasting to the leading strand wherein the DNA can be created continuously the lagging strand is synthesised discontinuously in the form of short fragments called Okazaki fragments. Okazaki fragments are the ones that are later associated covalently to form a continuous strand. This is since DNA synthesis can continue only in a single direction — the 5′ to 3′ direction.

The leading strand can easily be extended in an unceasing way in a similar way as the helix must open to permit exposure of templates for polymerization. On the other hand, the lagging strand must be intermittently extended away from the opening helix. This can only be achieved if the strand is completed discontinuously. The strand is synthesised in short segments and it is known as Okazaki fragments, named after its discoverers, the segments are later joined. This prerequisite has two essential significances:

1 – The lagging strand must have advanced priming and fragment connection mechanisms including several supplementary steps and reactions than needed for leading-strand extension.

2 – The Mechanisms of lagging-strand replication must have developed means of avoiding mutagenesis while managing the essential strand handlings.

The function of Okazaki Fragments

One significant role that Okazaki fragments play is in enabling the DNA polymerase to synthesise the lagging strand in spite of it being concerned with the opposite direction. Once both leading and lagging strands have been completed, another type of DNA polymerase, DNA polymerase I, comes in and gets rid of the RNA primers and substitutes them with DNA. The Okazaki fragments must be attached together into one continuous strand after replication. This is achieved by the enzyme DNA ligase, which seals the sugar-phosphate backbone of the Okazaki fragments. Thus, this permits for the replication of two, continuous identical daughter strands of DNA.

It can be said that the duplication of DNA is crucial before the cell division, wherein one parent cell can divide to form two daughter cells. This confirms that both daughters’ cells have precisely similar genetic material. In unicellular organisms, cell division can be a way of asexual reproduction. In multicellular organisms, cell division is crucial for the growing and reparation of the organism and for creating the cells required for sexual reproduction.

Conclusion

It can be concluded that Okazaki fragments processing is one of the most significant and basic processes of life. The process can be optimised in any specific organism for speed, fidelity, energy consumption, or some combination. Okazaki fragments can be explained as the fragments of DNA which are temporary components of lagging DNA combination at the replication fork. The discoverers of Okazaki fragments are Reiji Okazaki, Tsuneko Okazaki, along with their colleagues who first discovered the Okazaki fragments whilst they were studying the duplication of bacteriophage DNA in Escherichia coli in 1968. Thus, Okazaki fragments are named after its discoverers Reiji Okazaki and Tsuneko Okazaki. As mentioned above, Okazaki fragments serve essential functions in the body.