The main difference between the replication fork and replication bubble is that the replication fork occurs in the eukaryotic DNA replication, whereas the replication bubble occurs in the prokaryotic DNA replication.
Replication fork and replication bubble are two types of structures occurring in DNA molecules during replication. Both move during DNA replication.
Key Areas Covered
1. What is Replication Fork
– Definition, Structure, Function
2. What is Replication Bubble
– Definition, Structure, Function
3. Similarities Replication Fork and Replication Bubble
– Outline of Common Features
4. Difference Between Replication Fork and Replication Bubble
– Comparison of Key Differences
Key Terms
Replication Bubble, Replication Fork
What is Replication Fork
The replication fork is a structure forming in the long helical DNA during replication. The enzyme responsible for the creation of the replication fork is DNA helicase. This enzyme breaks the hydrogen bonds that hold the two DNA strands together. The replication fork contains two branching prongs, one with a single strand of DNA, that serves as the template for DNA replication. Here, the DNA strand with 5’ to 3’ direction serves as the leading strand with a continuous DNA replication towards the 5’ to 3’ direction. Whereas, the DNA strand with a 3’ to 5’ direction is the lagging strand with discontinuous DNA replication forming the Okazaki fragments. These fragments require DNA polymerase and ligase to form a continuous DNA strand.
Figure 1: Replication Fork
Furthermore, the DNA helicase is the enzyme responsible for the unwinding of DNA at the replication fork. Apart from that, RNA primase is the enzyme responsible for the short complementary RNA primers for the initiation of replication. Most importantly, the replication fork occurs in the eukaryotic DNA replication. Eukaryotes contain long helical DNA that is linear. Therefore, DNA replication starts from one end and ends up at the other end of the linear chromosomes.
What is Replication Bubble
The replication bubble is the structure that occurs in prokaryotic DNA replication. Prokaryotes contain single, circular DNA in their genome. These circular DNA molecules contain several origins of replication. Therefore, a single DNA molecule undergoes replication in more than one replication origin during replication. Each origin of replication contains a replication bubble. A replication bubble contains two replication forks that proceed in opposite directions. The prokaryotic chromosome contains several such replication bubbles.
Figure 2: Replication Bubble
Moreover, the area where the DN unwound for the replication in prokaryotes is called the replication bubble. It is Y-shaped and contains two replication forks. Each DNA strand in the unwound DNA serves as the template for DNA replication.
Similarities Between Replication Fork and Replication Bubble
- The replication fork and replication bubble are two structures that occur in DNA during DNA replication.
- Both contain DNA unwinding proteins as well as DNA polymerase enzyme along with DNA.
- Both structures move forward during replication.
Difference Between Replication Fork and Replication Bubble
Definition
The replication fork refers to the point at which the two strands of DNA are separated to allow the replication of each strand, while the replication bubble refers to an unwound, open region of the DNA helix where the DNA replication occurs.
Occurrence
The replication fork occurs in the eukaryotic DNA replication, while the replication bubble occurs in the prokaryotic DNA replication.
Type of DNA
Moreover, the replication fork occurs in linear DNA molecules, such as eukaryotic chromosomes, while the replication bubble occurs in circular DNA molecules, such as prokaryotic chromosomes.
Replication Origin
The replication fork contains a single replication origin, while the replication bubble contains two replication origins.
Movement
The replication fork moves forward while the replication bubble moves in opposite directions.
Conclusion
In brief, replication fork and replication bubble are two types of structures that occur in DNA during replication. The replication fork occurs in the eukaryotic DNA replication, specifically in linear DNA molecules such as eukaryotic chromosomes. In addition, it moves in the forward direction. In comparison, the replication bubble occurs in prokaryotic DNA replication. It has two replication origins and moves in opposite directions during replication. It occurs in circular DNA, such as prokaryotic chromosomes. Hence, the main difference between the replication fork and replication bubble is their occurrence.
References:
- DNA replication. Wikipedia. Wikimedia Foundation.
- DNA replication: Prokaryotes. The Biotech Notes.
Image Courtesy:
- “Replication fork” By Masur– Own work (CC-BY 2.5) via Commons Wikimedia
- “DNA bubbles.” By Boumphreyfr- Own Work (CC-BY SA 3.0) via Commons Wikimedia
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