Question

DNA replication in bacteria occurs:

• A. Within nucleolus
• B. Prior to fission
• C. Just before transcription
• D. During S phase

Answer 1

The Correct Option is B

To understand when DNA replication occurs in bacteria, let's explore the key stages of the bacterial cell cycle. 

1. Understanding Bacterial Cell Cycle: Bacterial cells, unlike eukaryotic cells, do not undergo a typical cell cycle with distinct phases such as G1, S, G2, and M. Instead, they replicate and divide through a simpler process known as binary fission.
2. Process of Binary Fission: Binary fission is the primary method of reproduction in bacteria where the cell divides into two identical cells. This process includes:
   • DNA replication
   • Segregation of the replicated DNA
   • Cytokinesis
3. Timing of DNA Replication: DNA replication in bacteria occurs before the cell actually divides, i.e., prior to the physical separation of the newly formed daughter cells. This ensures that each daughter cell receives an exact copy of the genetic material.
4. Analysis of Options:
   • Within nucleolus: This option is incorrect as bacteria do not have a nucleolus. The nucleolus is a feature of eukaryotic cells, where ribosomal RNA synthesis occurs.
   • Prior to fission: This is the correct option. In bacteria, DNA replication occurs before the cell divides when preparing for binary fission.
   • Just before transcription: This option is incorrect. DNA replication is a separate process from transcription, which involves making RNA from DNA. These processes can occur independently depending on the cell's needs.
   • During S phase: This option is incorrect for bacteria. The S phase is a part of the eukaryotic cell cycle, not applicable to bacterial cells.

Therefore, the correct answer is Prior to fission. Bacteria replicate their DNA before cell division takes place to ensure successful replication and segregation into two daughter cells.