Microbial genetics – transformation, transduction, conjugation MCQs With Answer

Microbial genetics — transformation, transduction, and conjugation — describes mechanisms by which bacteria exchange genetic material. For B.Pharm students this topic links fundamental processes (plasmids, bacteriophages, competence, conjugative pili) to clinical concerns like antibiotic resistance, virulence factor spread, and biotechnology applications such as recombinant DNA and vaccine design. Understanding transformation (uptake of naked DNA), bacteriophage-mediated transduction (generalized and specialized), and plasmid-driven conjugation (F-plasmid, Hfr, tra genes, type IV secretion) is essential for interpreting lab techniques (electroporation, CaCl2 treatment), mapping bacterial genomes, and controlling horizontal gene transfer in healthcare. These MCQs emphasize mechanisms, examples, clinical significance, and experimental methods to prepare you for exams and practical pharmacy work. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the defining feature of transformation in bacteria?

• Transfer of DNA via bacteriophages
• Transfer of plasmids through a sex pilus
• Uptake of free extracellular DNA from the environment
• Movement of transposons within the genome

Correct Answer: Uptake of free extracellular DNA from the environment

Q2. Which factor is essential for natural competence in many Gram-positive bacteria?

• Type IV secretion system
• Competence-stimulating peptide (CSP)
• Bacteriophage lysogeny
• Conjugative pili

Correct Answer: Competence-stimulating peptide (CSP)

Q3. Generalized transduction differs from specialized transduction because generalized transduction:

• Transfers only phage genes integrated at a specific site
• Transfers random fragments of bacterial DNA packaged by mistake
• Requires the F-plasmid for transfer
• Occurs only in lysogenic cycles

Correct Answer: Transfers random fragments of bacterial DNA packaged by mistake

Q4. In conjugation, an Hfr strain is best described as:

• A cell carrying a non-transferable plasmid
• A cell with an F-plasmid integrated into the chromosome
• A bacteriophage-infected lysogen
• A naturally competent cell taking up DNA

Correct Answer: A cell with an F-plasmid integrated into the chromosome

Q5. Which laboratory method is commonly used to artificially induce transformation in E. coli?

• Transduction with lambda phage
• Electroporation
• Conjugation with an Hfr donor
• CRISPR-Cas9 delivery without plasmids

Correct Answer: Electroporation

Q6. A bacteriophage that follows the lytic cycle typically:

• Integrates into the host genome and remains dormant
• Immediately replicates and lyses the host cell
• Transfers plasmids via pili
• Converts bacteria to a competent state

Correct Answer: Immediately replicates and lyses the host cell

Q7. Which of the following best explains specialized transduction?

• Random bacterial DNA is packaged due to headful packaging errors
• A prophage excises imprecisely and carries adjacent bacterial genes
• DNA is transferred through a conjugative pilus
• Free plasmid DNA is taken up by competent cells

Correct Answer: A prophage excises imprecisely and carries adjacent bacterial genes

Q8. The F plasmid contains tra genes. What is the primary role of tra genes?

• Encode restriction enzymes to degrade foreign DNA
• Mediate pilus formation and DNA transfer during conjugation
• Promote lysogenic conversion by phages
• Enable uptake of naked DNA during transformation

Correct Answer: Mediate pilus formation and DNA transfer during conjugation

Q9. Which mechanism is a major contributor to the spread of antibiotic resistance between bacterial species in hospitals?

• Natural selection without gene transfer
• Vertical transmission only
• Horizontal gene transfer via plasmids and transposons
• Spontaneous point mutations exclusively

Correct Answer: Horizontal gene transfer via plasmids and transposons

Q10. Specialized transduction is commonly associated with which type of phage lifecycle?

• Lytic lifecycle only
• Lysogenic lifecycle with prophage integration
• Plasmid-mediated lifecycle
• Conjugative lifecycle

Correct Answer: Lysogenic lifecycle with prophage integration

Q11. In bacterial conjugation, what is oriT?

• The origin of chromosomal replication
• The origin of transfer on a conjugative plasmid where nicking initiates transfer
• The phage attachment site on the bacterial chromosome
• The promoter for tra gene expression

Correct Answer: The origin of transfer on a conjugative plasmid where nicking initiates transfer

Q12. Which of the following best describes a transducing particle?

• An intact plasmid packaged by conjugation
• A bacteriophage particle that contains bacterial DNA instead of phage DNA
• A naked DNA fragment taken up during transformation
• A mobile genetic element that self-replicates like a plasmid

Correct Answer: A bacteriophage particle that contains bacterial DNA instead of phage DNA

Q13. Conjugative transposons differ from simple transposons because they:

• Cannot move between cells
• Encode functions for excision, transfer, and integration into new cells
• Only move via bacteriophage intermediates
• Require electroporation to transfer between bacteria

Correct Answer: Encode functions for excision, transfer, and integration into new cells

Q14. Which experimental observation would best indicate that gene transfer occurred by transformation rather than conjugation?

• Transfer required direct cell-to-cell contact
• DNase treatment of the medium abolishes transfer
• Transfer depended on functional tra genes
• Transfer occurred only when phage was present

Correct Answer: DNase treatment of the medium abolishes transfer

Q15. Which genetic element often carries multiple antibiotic resistance genes and can move between bacteria via conjugation?

• Integron with gene cassettes located on a plasmid
• rRNA operon on the chromosome
• Riboswitch-controlled metabolic gene
• Single-copy housekeeping gene

Correct Answer: Integron with gene cassettes located on a plasmid

Q16. Mapping bacterial genes by conjugation using Hfr strains is based on:

• Frequency of generalized transduction events
• Time of entry of specific markers into the recipient cell during mating
• Rate of spontaneous mutation in auxotrophic strains
• Ability of phage to package headful DNA

Correct Answer: Time of entry of specific markers into the recipient cell during mating

Q17. Which statement about plasmid replication during conjugation is correct?

• Plasmids are transferred as double-stranded circular DNA without replication
• Rolling-circle replication in the donor replaces the transferred strand while the recipient synthesizes the complementary strand
• Replication of plasmids only occurs in the recipient after transfer completes
• Plasmids replicate by host chromosome-originated bidirectional replication during transfer

Correct Answer: Rolling-circle replication in the donor replaces the transferred strand while the recipient synthesizes the complementary strand

Q18. Lysogenic conversion can result in which clinically important change in a bacterial host?

• Loss of all plasmids
• Acquisition of toxin genes encoded by a prophage
• Immediate cell lysis and death
• Becoming unable to undergo transformation

Correct Answer: Acquisition of toxin genes encoded by a prophage

Q19. Which of the following increases the efficiency of artificial transformation in laboratory strains?

• Treating cells with CaCl2 or using electroporation
• Exposing cultures to UV light to induce competence
• Adding bacteriophages during transformation
• Using conjugative F+ donor strains

Correct Answer: Treating cells with CaCl2 or using electroporation

Q20. In generalized transduction, which enzymes or events primarily cause bacterial DNA to be packaged into phage heads?

• Site-specific recombination at att sites
• Random DNA fragmentation and erroneous packaging during phage assembly
• Conjugative transfer through pili
• Homologous recombination between plasmids

Correct Answer: Random DNA fragmentation and erroneous packaging during phage assembly

Q21. An R plasmid is best defined as:

• A plasmid carrying genes for restriction-modification systems
• A plasmid that confers antibiotic resistance
• A plasmid essential for host survival
• A chromosomal island carrying virulence genes

Correct Answer: A plasmid that confers antibiotic resistance

Q22. What role do integrons play in antimicrobial resistance?

• They synthesize antibiotics to which bacteria become resistant
• They capture and express gene cassettes, often encoding resistance determinants
• They prevent conjugation by blocking pilus assembly
• They package bacterial DNA into phage heads during transduction

Correct Answer: They capture and express gene cassettes, often encoding resistance determinants

Q23. Which experimental approach distinguishes generalized from specialized transduction in a bacteriophage preparation?

• Sequencing the phage capsid proteins
• Determining whether multiple different, unlinked bacterial genes are transduced
• Measuring antibiotic susceptibility of donor cells
• Assessing the presence of the F-plasmid in the donor

Correct Answer: Determining whether multiple different, unlinked bacterial genes are transduced

Q24. Conjugation in Gram-negative bacteria typically uses which secretion system for DNA transfer?

• Type I secretion system
• Type IV secretion system
• Type III secretion system
• Type VI secretion system

Correct Answer: Type IV secretion system

Q25. If DNase treatment does not reduce gene transfer frequency between two strains, the most likely mechanism of transfer is:

• Transformation
• Conjugation or transduction (protected by cell contact or phage particle)
• Uptake of naked DNA from the medium
• Spontaneous chromosomal crossovers without DNA movement

Correct Answer: Conjugation or transduction (protected by cell contact or phage particle)

Q26. Which of the following is a clinical implication of phage-mediated horizontal gene transfer?

• Phages always reduce bacterial virulence
• Phages can disseminate toxin or antibiotic resistance genes among pathogens
• Phage infection prevents conjugation entirely
• Phage therapy eliminates the risk of gene transfer

Correct Answer: Phages can disseminate toxin or antibiotic resistance genes among pathogens

Q27. Which molecular event is required for stable integration of transforming DNA into the recipient chromosome?

• Non-homologous end joining exclusively
• Homologous recombination between donor and recipient sequences
• Conjugative transfer through tra proteins
• Immediate circularization into a plasmid form without recombination

Correct Answer: Homologous recombination between donor and recipient sequences

Q28. A phage particle that has packaged bacterial DNA and is incapable of initiating a normal lytic cycle is called:

• A prophage
• A defective transducing particle
• An Hfr phage
• A conjugative plasmid

Correct Answer: A defective transducing particle

Q29. In the context of recombinant DNA techniques used in pharmacy research, which gene transfer method is most commonly used to introduce plasmids into bacterial cloning strains?

• Natural transduction by wild phages
• Artificial transformation (e.g., CaCl2 treatment or electroporation)
• Conjugation from clinical isolates
• Spontaneous chromosomal integration without vectors

Correct Answer: Artificial transformation (e.g., CaCl2 treatment or electroporation)

Q30. Which statement best summarizes why B.Pharm students must understand microbial horizontal gene transfer?

• It is only of theoretical interest with no practical consequences
• It explains mechanisms of drug resistance spread, impacts therapeutic strategies, and informs safe use of recombinant techniques
• It is irrelevant because antibiotics remove all resistant strains
• It only applies to viruses and not to bacteria

Correct Answer: It explains mechanisms of drug resistance spread, impacts therapeutic strategies, and informs safe use of recombinant techniques

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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