What are plasmids? Where are they present?
GeneralClass 12AllAnswered 27 Mar 2026
Answer
Plasmids are extra-chromosomal, circular, double-stranded DNA molecules in prokaryotic cells.
Location: Bacterial cytoplasm, independent of chromosomal DNA
Characteristics:
- Size: 1–200 kb (kilobases)
- Self-replicating (autonomous replication)
- Carry non-essential genes: antibiotic resistance (R-plasmids), virulence factors, metabolic enzymes, nitrogen fixation
Significance:
- Horizontal gene transfer (conjugation)
- Genetic engineering tools (cloning vectors, expression systems)
- Antibiotic resistance spread (public health concern)
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