Prokaryotic vs Eukaryotic DNA Replication
According to the Watson and Crick model suggested for DNA, one strand of DNA is the complement of the other strand; hence each strand acts as a template for the formation of a new strand of DNA. This process is known as DNA replication. The replication of DNA basically involves the unwinding of the parent strands and the base pairing between the two new strands, so that each new DNA molecule contains one new and one old strand, which belongs to parent DNA molecule. DNA replication is very complex process and involves many cellular functions and certain verification procedures. DNA polymerase is the main enzyme involved in DNA replication. The basic two types of replication are conservative replication and semiconservative replication. Prokaryotic DNA and eukaryotic DNA vary widely; so do their replication processes.
Prokaryotic DNA Replication
Unlike in eukaryotes, there is a single circular DNA exists in prokaryotes. The replication in the prokaryotic chromosome begins at the origin of replication. At the beginning of replication, enzyme breaks the hydrogen bonds between the two parent strands of DNA at the origin of replication, establishing the replication fork. After the formation of replication fork, the strands of the double helix begin to unwind and separate from each other. While the unwinding takes place, the DNA polymerase begins the synthesis of new DNA strand by adding nucleotides. As the replication proceeds, the replication forks travels in the opposite direction. After the completion of replication, each new double stranded DNA contains one old DNA and one new DNA. Once the two DNA molecules have formed, the cell is ready for binary fission.
Eukaryotic DNA Replication
Unlike in prokaryotes, eukaryotes have a large amount DNA. Therefore, the replication of DNA in eukaryotes are quite complex and involve many biological processes. Since the DNA amount is large, there are few origins of replication points, which form the bubbles. In these areas, enzymes break the strands and begin to transcribe in opposite directions on each site of the DNA molecule. Here, the DNA polymerase synthesizes two new strands of DNA. As the replication proceeds, new nucleotides are added to the growing DNA molecule. The replication process completes when the replication forks meet each other. Once the replication process is complete, the cell is ready for the mitosis.
What is the difference between Prokaryotic and Eukaryotic DNA Replication?
• Duration of DNA replication in eukaryotes is longer than that in prokaryotes.
• In eukaryotes, multiple replication sites are present in a single DNA molecule whereas, in prokaryotes, a single replication site is present in the circular DNA molecule.
• In prokaryotes, DNA replication involves three polymerase enzymes; namely, DNA polymerase I, DNA polymerase II, and DNA polymerase III. In contrast, DNA replication of eukaryotes involve four types of polymerase enzymes; namely, α, β, γ, and δ.
• Functional variety of DNA polymerase is specific in eukaryotes, whereas it is diverse in prokaryotes.
• In eukaryotes, β- polymerase functions as a repair enzyme, whereas there is no such repair function in prokaryotes.
• In prokaryotes, few replication forks are formed whereas, in eukaryotes, many replication forks are formed.
• In prokaryotes, theta structure is observed whereas, in eukaryotes, it is not observed.
• In eukaryotes, many accessory proteins with diverse functions are involved whereas, in prokaryotes, few accessory proteins with limited functions are involved.
• Histone separation and unwinding take place in eukaryotes, while only unwinding takes place in prokaryotes.
• Many replication bubbles present in eukaryotes, whereas no or few replication bubbles present in prokaryotes.
• In prokaryotes, RNA acts as the primer whereas, in eukaryotes, either RNA or DNA acts as the primer.
• DNA replication in eukaryotes takes place during the cell cycle, unlike in prokaryotes.