The Concept of Okazaki Fragments

During DNA replication, Okazaki fragments (which are approximately 150 to 200 base pairs long in eukaryotes) are short sequences of DNA nucleotides that are synthesised in a discontinuous manner and later linked together by the enzyme DNA to form the lagging strand, which is known as the lagging strand syndrome. 

Okazaki Fragments

When a cell divides, the genetic information contained in the lengthy strands of DNA that make up the cell is replicated by enzymes known as DNA polymerases, which are found in every cell in the body. In the case of DNA, each strand generates a template, which is then utilised by the DNA polymerases to synthesise the complementary strand. When the replication fork is formed, one strand (leading strand) is continuously synthesised in the 5′ to 3′ direction, while the second strand (lagging strand) is discontinuously synthesised in the 3′ to 5′ direction in short pieces that are referred to as Okazaki fragments.

It is believed that Japanese molecular researchers Reiji Okazaki and Tuneko Okazaki, along with the assistance of some of their colleagues, were the ones who found these pieces in the 1960s.

Okazaki Fragments are defined as follows:

Okazaki fragments are small segments of DNA that are formed when the lagging strand undergoes discontinuous replication, as in the case of a DNA strand break.

The length of these pieces in bacterial cells is between 1000 and 2000 nucleotides, whereas the length of these fragments in eukaryotic cells ranges between 100 and 200 nucleotides. Using the Okazaki fragments on the lagging strand, it is possible to produce a continuous new molecule of DNA on the leading strand.

Causes of Formation of Okazaki Fragments

The genetic material in the majority of the entities is represented by DNA. The DNA molecule is double-stranded, consisting of two DNA strands that run antiparallel to one another and are joined together by hydrogen bonds. Cell division necessitates the replication of the whole genome, which results in a doubling of the DNA found in the original cell at the moment of division. At the cellular level, DNA replication occurs in a semi-conservative fashion where one of the strands in the newly generated DNA (which is double-stranded) is the parent strand, or the original strand. As a result, both strands of DNA must serve as templates in the process of DNA replication. DNA polymerases are enzymes that play a role in the replication of genetic material. They can only synthesise DNA in the direction of 5′ to 3′ strands of DNA. Nevertheless, because of the antiparallel structure of double-stranded DNA, DNA synthesis must occur in either direction. As a result, when the trailing template strand is synthesised, the fragments take shape at the same moment.

In most cases, the DNA polymerase adds nucleotides in the direction of 5′ to 3′ amplification. The enzymes are capable of continuously adding nucleotides to the expanding strand on the leading strand, which is a characteristic of the leading strand. Because the strand is flowing in the direction of 5′ to 3′, the expansion of the chain of the freshly synthesised strand of DNA is halted when it reaches the 5′ terminus of the strand, which is the 5′ terminal of the strand. The replication fork is the point at which the synthesis of yet another DNA begins.

In double-stranded DNA, this fork is the point where the unwinding process begins, which is critical in the synthesis of new strands of DNA on the parent strands of the double-stranded DNA. During the transition from the single-stranded to double-stranded state, DNA polymerase can link nucleotides present on the trailing strand together. However, when the synthesis reaches the 5′ terminal of the RNA primer of the stretch of DNA that has already been synthesised, the synthesis is terminated. A result of this is that DNA is not continuously synthesised at the lagging strand, with long segments of DNA being produced as Okazaki fragments as a result of this.

Formation of the Okazaki Fragments

In order for the DNA polymerase to synthesise a section and then wait for the helicase to open up more of the DNA helix upstream, Okazaki fragments are generated on the lagging strand of the DNA polymerase’s reaction. Following the helicase’s opening up of the DNA, the primase enters and places a new complementary RNA primer, which allows the DNA polymerase to join the DNA and generate the new Okazaki fragment.

Function of Okazaki Fragments 

Although it is orientated in the opposite direction of the leading strand, Okazaki fragments are essential for the DNA polymerase to be able to synthesise the lagging strand successfully. A kind of DNA polymerase known as DNA polymerase enters the cell and eliminates the RNA primers, allowing DNA to take their place. Once replication has taken place, the Okazaki fragments should be joined together to form a single continuous strand. This is accomplished through the action of the DNA ligase, which binds the sugar-phosphate backbone of the Okazaki fragments together. This allows for the replication of two identical daughter DNA strands that are continuous throughout the process.

When a parent cell divides to produce two daughter cells, it is critical that the DNA of both daughter cells be replicated before cell division can take place. This ensures that both daughter cells receive the same genetic material. Cell division in unicellular entities could be a means of asexual reproduction, whereas cell division in multicellular entities is essential for the repair and expansion of the entity as well as for the generation of cells required for sexual reproduction in multicellular entities.

Use of  Okazaki Fragments 

Okazaki fragments are small portions of DNA that are generated during the replication of DNA when the lagging strand undergoes discontinuous synthesis for a short period of time. It is required for cell division because it enables for the synthesis of both daughter strands that are required for cell division.

As the DNA polymerase is not correctly oriented for continuous synthesis, the Okazaki fragments serve to allow the polymerase to synthesise the lagging strands in the segments, which would otherwise be impossible.

Conclusion

When a cell divides, the genetic information contained in the lengthy strands of DNA that make up the cell is replicated by enzymes known as DNA polymerases, which are found in every cell in the body.Okazaki fragments are small segments of DNA that are formed when the lagging strand undergoes discontinuous replication, as in the case of a DNA strand break.It is required for cell division because it enables for the synthesis of both daughter strands that are required for cell division.Okazaki fragments are generated on the lagging strand of the DNA polymerase’s reaction.Although it is orientated in the opposite direction of the leading strand, Okazaki fragments are essential for the DNA polymerase to be able to synthesise the lagging strand successfully.