Which of the following is incorrect regarding DNA replication forks?

• A. DNA replication forks begin forming at the origin of replication (ORI).
• B. DNA replication forks are caused by helicase separating two complementary strands of DNA.
• C. There are two replication forks found in each replicating prokaryotic chromosome.
• D. DNA replication forks are found at both ends of the replication 'bubble'.
• E. None of the above are incorrect.

Answer: (E)

Verified step by step guidance

1. Understand the concept of a DNA replication fork: A DNA replication fork is a structure that forms within the nucleus during DNA replication. It is created by helicases, which break the hydrogen bonds holding the two DNA strands together, allowing each strand to be copied.
2. Identify the origin of replication (ORI): The ORI is a specific sequence in the genome where replication begins. In prokaryotes, there is typically a single ORI, while eukaryotes have multiple ORIs.
3. Examine the role of helicase: Helicase is an enzyme that unwinds the DNA double helix, creating two single strands that serve as templates for replication. This action forms the replication fork.
4. Consider the number of replication forks in prokaryotic chromosomes: In prokaryotic cells, such as bacteria, the circular DNA typically has two replication forks that move in opposite directions from the ORI, eventually meeting at the opposite side of the circle.
5. Understand the replication 'bubble': As the DNA unwinds, a replication 'bubble' forms, with replication forks at each end. This bubble expands as replication proceeds, allowing the entire DNA molecule to be replicated.