Vector Biology Assessment Questions and Answers focuses on “Vectors for Mammals – 6”.
1. Agrobacterium tumefaciens can transfer DNA to animal cells.
A. True
B. False
Answer: A
Clarification: A. tumefaciens and its close relatives have been used for over 20 years to generate transgenic plants. More recently, it has been shown that A. tumefaciens can transfer DNA to cultured human cells.
2. Which of the following is an artificial form of bactofection?
A. Transduction
B. Protoplast fusion
A. Bolistics
D. Electroporation
Answer: B
Clarification: The protoplast fusion technique can be regarded as a highly artificial form of bactofection, but the amount of human intervention required distinguishes the technique.
3. In the cases of Salmonella species, lysis occurs in the __________
A. Outside the phagocytic vesicle
B. Inside the phagocytic vesicle
A. In lymphatic system
D. In nucleus
Answer: B
Clarification: In the case of Salmonella species, lysis occurs in the phagocytic vesicle, while for other species lysis occurs after the bacterium has escaped from the vesicle.
4. Which of the following occurs in DNA transfer by A. Tumefaciens?
A. Cell lysis
B. Conjugation
A. Infection
D. Myeloma
Answer: B
Clarification: A. tumefaciens transfers DNA to mammalian cells without invading them. Transfer occurs by attachment to the outside of the cell followed by conjugation.
5. Pilus helps in the transfer of DNA through a process of ___________
A. Transduction
B. Transfection
A. Conjugation
D. Transformation
Answer: C
Clarification: In A. tumefaciens, transfer occurs by attachment to the outside of the cell followed by conjugation. It is a process of transfer of DNA through a conduit called a pilus, which is assembled by the bacterial cell.
6. Which is an important principle in gene transfer using live bacteria?
A. Amplification
B. Attenuation
A. Lysis
D. Phagocytosis
Answer: B
Clarification: An important principle in the use of live bacteria as invasive gene-transfer vehicles is that they must be attenuated.
7. What would happen if attenuated bacteria are not used for mammalian gene transfer?
A. Cell death
B. Tumor
A. Proliferation
D. Unsuccessful gene transfer
Answer: A
Clarification: The gene transfer system exploits the natural ability of the bacteria to infect and subvert the activity of eukaryotic cells. Without attenuation, the bacteria would multiply and destroy the host cells.
8. Which of the following is a technique of bacterial attenuation?
A. Auxotrophic mutants
B. Removal of cell wall
A. Protoplast fusion
D. Conjugation
Answer: A
Clarification: Attenuation is achieved in several ways. One way is to use auxotrophic mutants that are bacterial strains that are unable to manufacture essential molecules.
9. AroA mutants are unable to synthesize _____________
A. Amino acids
B. Homeotic genes
A. Vitamins
D. Aromatic compounds
Answer: D
Clarification: AroA mutants are unable to synthesize aromatic amino acids and Salmonella typhimurium and Shigella flexneri strains carrying this mutation have been used for gene transfer.
10. Inducible autolysis is a technique for attenuation.
A. True
B. False
Answer: A
Clarification: The bacteria can be engineered so that they undergo inducible autolysis. Attenuation can be achieved by induced suicide, introducing an autolysin-encoding gene that is activated once the bacterium is inside the host cell.
11. Attenuation of ‘Listeria Monocytogenes’ can be achieved by ___________
A. Auxotrophic strains
B. Autolysis
A. Gene knockout
D. Mutation
Answer: B
Clarification: There are no auxotrophic strains of Listeria monocytogenes, so attenuation is achieved by induced suicide. Autolysin-encoding gene is introduced.
12. Apart from the introduction of DNA into cultured cells, bacteria mediated gene transfer has also been used for ________
A. Recombinant protein production
B. Transgenic animal
A. In vivo gene transfer
D. In vitro gene transfer
Answer: C
Clarification: Bacteria mediated gene transfer has been used not only as general transfection method for the introduction of DNA into cultured cells but also as a high efficiency method for gene transfer in vivo.
13. Virus particles have a natural ability of ___________
A. Adsorbing on the cell surface
B. Proliferation
A. Inducing tumor
D. Inducing apoptosis
Answer: A
Clarification: Virus particles have a natural ability to adsorb to the surface of cells and gain entry, and this can be exploited to deliver recombinant DNA into animal cells.
14. Helper-independent vectors can _____________
A. Not Propagate
B. Propagate dependently
A. Propagate independently
D. Transduce the cell
Answer: C
Clarification: If the transgene is added to the genome, or if it replaces one or more genes that are non-essential for the infection cycle in the expression host being used, the vector is described as helper-independent because it can propagate independently.
15. What happens if an essential gene is replaced in a viral vector?
A. Helper dependent
B. Helper independent
A. Non-function
D. Loss of transfection ability
Answer: A
Clarification: If the transgene replaces an essential viral gene, this renders the vector helper-dependent so that missing functions must be supplied in trans.
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