Initiation of DNA replication requires many proteins to interact with DNA to begin replication. Prokaryotes have a single DNA sequence to begin DNA replication. 
Important terms in prokaryotic initiation:
- Origin of replication
- Topoisomerase II
- DNA Polymerase III

Initation of DNA Replication in Prokaryotes

Termination of replication occurs after the chromosome has been replicated. Uniquely in prokaryotes, topoisomerase IV is important in the termination of DNA replication. 
Key term in prokaryotic termination of replication:
- Topoisomerase IV

Termination of DNA Replication in Prokaryotes

Elongation of DNA replication requires adding the DNA bases of the elongating strands. The primers introduced in initiation are also removed. 
Key terms in prokaryotic elongation:
- DNA Polymerase I

Elongation of DNA Replication in Prokaryotes

DNA replication in bacteria occurs rapidly at approximately 1000 nucleotides per second, which is approximately ten times the speed of eukaryotes. It also occurs at a single origin to begin replication.

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The steps of DNA replication are shared between eukaryotes and prokaryotes. The steps of DNA replication are: 
1. Initiation
2. Elongation
3. Termination

The Steps of DNA Replication

While eukaryotes and prokaryotes have some differences between their processes of DNA replication, they share many of the same proteins needed for replication. These are: 

- DNA Polymerase
- Helicase
- Topoisomerase
- Sliding Clamp
- Primase
- Single-stranded binding protein
- Ligase

Enzymes Involved in DNA Replication

DNA Replication shares many of the same enzymes and components across organisms. However, there are key difference between many of them.

Here we designate the different types of DNA replication: 
- Prokaryotic DNA Replication
- Eukaryotic DNA Replication

Classifications of DNA Replication by the Domains of Life

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DNA Replication in Prokaryotes

Initiation of DNA replication involves many proteins to interact with the DNA to make it accessible to be replicated. In prokaryotes, there is one DNA sequence where initiation can begin but in eukaryotes there are many.

Initiation of DNA Replication

Elongation of DNA replication involves adding nucleotides to the DNA towards the direction of the replication fork. This is done by DNA polymerase.

Elongation of DNA Replication

The end of DNA replication must involve sealing of the DNA at the replication fork to make double stranded replicated DNA.

Termination of DNA Replication

Helicase separates the DNA strands by severing the hydrogen bonds between the DNA base pairs at the origin of replication. This requires ATP for energy. This creates the replication fork which are at each end of the replicating DNA.

Helicase

The sliding clamp protein keeps DNA polymerase in place while it synthesizes DNA.

Sliding Clamp

DNA ligase joins the Okazaki fragments on the newly synthesized DNA of the lagging strand by forming the phosphodiester linkages between the DNA fragments.

DNA ligase

RNA Primase adds a primer to the DNA to begin replication. This is necessary because DNA polymerase requires a 3'-hydroxyl group to add nucleotides for DNA replication. RNA Primase provides this 3'-hydroxyl by adding a short strand of RNA with a 3'-hydroxyl end to the single stranded DNA. 

RNA Primase

Single-stranded binding proteins (SSBs) coat the single-stranded DNA to ensure it does not prematurely rewind into a helix during DNA replication. 

Single-stranded binding proteins (SSBs)

Topoisomerase is responsible for relaxing DNA to begin DNA replication. They relax the DNA by making cuts in the DNA. 

Topoisomerase

There are several kinds of DNA Polymerases in eukaryotes and prokaryotes. DNA Polymerase adds nucleotides to DNA strands in replication.This process requires energy.

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