Question

The antibiotic "ciprofloxacin" used in the treatment of bovine mastitis helps control the infection by interfering with the bacterial

• A. Replication of DNA
• B. Transcription of DNA
• C. Translation of RNA
• D. Posttranslational modification of proteins

Hint:

Antibiotic Mechanisms:
Fluoroquinolones (Ciprofloxacin) $\rightarrow$ Inhibits DNA Gyrase (DNA Replication).
Rifampicin $\rightarrow$ RNA Polymerase (Transcription).
Aminoglycosides/Tetracyclines $\rightarrow$ Ribosomes (Translation).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Fluoroquinolone antibiotics selectively trap topoisomerase-DNA cleavage complexes, arresting replication fork progression and causing lethal double-stranded DNA breaks.
Key Formula or Approach:
\[ \text{Ciprofloxacin} \xrightarrow{\text{Inhibits}} \text{DNA Gyrase (Topoisomerase II) \& Topoisomerase IV} \implies \text{Halts DNA Replication} \]

Step 2: Detailed Explanation:
Ciprofloxacin is a broad-spectrum fluoroquinolone antibiotic:
- It selectively inhibits bacterial DNA Gyrase (type II topoisomerase) and Topoisomerase IV.
- DNA gyrase introduces negative supercoils ahead of the replication fork to relieve positive superhelical tension during DNA unwinding.
- Ciprofloxacin traps the covalent gyrase-DNA intermediate, stalling DNA replication forks and inducing catastrophic chromosomal fragmentation, thereby halting bacterial DNA replication.

Step 3: Final Answer:
Hence, ciprofloxacin acts by interfering with Replication of DNA, matching option (A).