Paper I — 2025 August (Supplementary) (2010 Scheme) — Q9

Paper I

2025 August (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Plasmids

Q92 marksShort Notes★✓

Answer

A plasmid is a small, extrachromosomal, double-stranded, circular DNA molecule capable of independent (autonomous) replication within a bacterial cell, distinct from the bacterial chromosome — not essential for basic survival, but often carrying genes that provide a selective advantage under specific conditions.

Types: F (fertility) plasmid — encodes genes for conjugation; R (resistance) plasmid — carries antibiotic-resistance genes; Col plasmid — encodes bacteriocins; virulence plasmids — carry toxin/virulence genes.

Clinical significance: plasmids, particularly R plasmids, are the principal vehicle for rapid horizontal spread of antibiotic resistance between bacteria, even across different species/genera, via conjugation — a single plasmid can carry resistance to multiple antibiotic classes simultaneously, making plasmid-mediated resistance a major driver of multidrug-resistant pathogens.

Related Concepts

1. 1Bacterial Genetics

Other Years Asked

1. 1Describe principles of genetic engineering and their applications.2022 February (2019 Scheme)Short Essay · 8 marks
2. 2Conjugation2023 July (Supplementary) (2010 Scheme)Short Essay · 5 marks
3. 3Transduction2022 May (Supplementary) (2010 Scheme)Short Note · 2 marks
4. 4Define plasmid. Give two clinical significance of plasmid.2023 March (Supplementary) (2010 Scheme)Short Note · 2 marks
5. 5R plasmid2013 April (2010 Scheme)Short Note · 2 marks
6. 6Transformation2022 October (Supplementary) (2010 Scheme)Short Note · 2 marks
7. 7Mutation.2017 February (2010 Scheme)Short Note · 2 marks
8. 8Transposons.2021 December (Supplementary) (2010 Scheme)Short Note · 2 marks
9. 9Name two horizontal gene transfer method in bacteria2025 March (Supplementary) (2010 Scheme)Short Note · 2 marks
10. 10Bacterial conjugation.2013 September (Supplementary) (2010 Scheme)Short Note · 2 marks
11. 11Transduction2016 February (2010 Scheme)Short Note · 2 marks
12. 12Transduction2014 March (2010 Scheme)Short Note · 2 marks
13. 13Plasmid2021 February (Supplementary) (2010 Scheme)Short Note · 2 marks
14. 14Enumerate methods of gene – transfer in bacteria2019 July (Supplementary) (2010 Scheme)Short Note · 2 marks
15. 15Mention two methods of extra chromosomal transfer of genetic material in bacteria2018 July (Supplementary) (2010 Scheme)Short Note · 2 marks
16. 16An example of extrachromosomal element is2024 December (Supplementary) (2019 Scheme)MCQ · 1 mark
17. 17Clinical importance of plasmids in bacteria with two examples.2023 January (Supplementary) (2019 Scheme)1 mark