Which statement correctly defines a transposon in bacterial genetics?
- A A mobile DNA segment flanked by insertion sequences that can move between plasmids and chromosomes ✓
- B A circular extrachromosomal DNA molecule that replicates autonomously and transfers by conjugation
- C A temperate bacteriophage genome integrated into the bacterial chromosome
- D A segment of chromosomal DNA transferred between bacteria by a lytic bacteriophage
Correct answer: A. A mobile DNA segment flanked by insertion sequences that can move between plasmids and chromosomes
Explanation
Transposons are mobile genetic elements carrying genes such as resistance determinants, bounded by insertion sequences that supply the transposase needed for excision and reinsertion. They move between sites within a replicon and between plasmid and chromosome without sequence homology. Option B describes a conjugative plasmid, option C a prophage, and option D generalized transduction, so none matches the definition of site-independent mobile elements.
Reference: Jawetz, Melnick & Adelberg's Medical Microbiology, 28th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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