Part 4: Competent Host & Methods of Gene Transfer (25 MCQs)
Part 4: Competent Host & Methods of Gene Transfer (25 MCQs)
Q76. The most commonly used host organism in recombinant DNA experiments is:
a) Bacillus subtilis
b) Escherichia coli
c) Saccharomyces cerevisiae
d) Agrobacterium tumefaciens
Answer: b
- b) Correct: E. coli is the most widely used host because it is well-studied, fast-growing, and easy to manipulate.
Q77. A host cell is made competent by:
a) Treating with CaCl₂
b) Heat shock
c) Electroporation
d) All of the above
Answer: d
- d) Correct: Competency can be induced by chemical (CaCl₂), heat shock, or electrical pulse methods.
Q78. The CaCl₂ method of competence works by:
a) Increasing plasmid replication
b) Neutralizing the negative charge of DNA and cell membrane
c) Destroying bacterial cell wall
d) Activating antibiotic resistance
Answer: b
- b) Correct: Ca²⁺ ions neutralize charges, allowing DNA entry.
Q79. Heat shock in E. coli transformation is done at:
a) 37°C
b) 0°C
c) 42°C
d) 25°C
Answer: c
- c) Correct: 42°C heat shock creates pores in membrane for DNA uptake.
Q80. Electroporation introduces DNA into cells by:
a) Heat denaturation
b) Creating transient pores with electric shock
c) Digesting cell wall
d) RNA splicing
Answer: b
- b) Correct: Short electric pulses create pores in membrane → DNA enters.
Q81. Which method is commonly used to introduce genes into plants?
a) Ti plasmid-mediated transfer
b) Biolistics (gene gun)
c) Electroporation
d) All of the above
Answer: d
- d) Correct: Ti plasmid, gene gun, and electroporation are all used in plants.
Q82. Biolistics (gene gun) involves:
a) Viruses
b) Gold or tungsten particles coated with DNA shot into cells
c) Electric current
d) Heat shock
Answer: b
- b) Correct: Gene gun uses DNA-coated particles shot into plant cells.
Q83. Microinjection of DNA is done into:
a) Plant leaf tissue
b) Animal cells or oocytes
c) Bacterial cells
d) Viruses
Answer: b
- b) Correct: Microinjection directly introduces DNA into animal cells/oocytes.
Q84. Agrobacterium tumefaciens transfers DNA via:
a) Ti plasmid (T-DNA region)
b) Viral infection
c) Heat shock
d) RNA interference
Answer: a
- a) Correct: T-DNA from Ti plasmid integrates into plant genome.
Q85. Which is NOT a method of gene transfer?
a) Conjugation
b) Biolistics
c) Microinjection
d) Electroporation
Answer: a
- a) Correct: Conjugation = natural gene transfer, not used in rDNA technology.
Q86. Which vector is used for monocot plant transformation?
a) Ti plasmid
b) Retrovirus
c) Gene gun (biolistic method)
d) Phage λ
Answer: c
- c) Correct: Gene gun is useful for monocots where Ti plasmid is less effective.
Q87. Competence means:
a) Ability of DNA to replicate
b) Ability of a host cell to take up foreign DNA
c) Presence of restriction sites
d) Loss of antibiotic resistance
Answer: b
- b) Correct: Competence = state where host cell can take foreign DNA.
Q88. Protoplast fusion is a method of gene transfer involving:
a) Heat shock
b) Fusion of two cells without cell walls
c) Virus-mediated DNA transfer
d) Protein synthesis
Answer: b
- b) Correct: Protoplast fusion → fusion of naked cells after cell wall removal.
Q89. Which method is used to introduce genes into animal cells using viruses?
a) Biolistics
b) Viral vectors
c) Microinjection
d) Heat shock
Answer: b
- b) Correct: Viruses (retrovirus, adenovirus) can deliver genes into animals.
Q90. Which of the following is NOT used for making plant cells competent?
a) Agrobacterium
b) Electroporation
c) Gene gun
d) Streptokinase
Answer: d
- d) Correct: Streptokinase = clot buster enzyme, not gene transfer tool.
Q91. Transformation in bacteria refers to:
a) Viral DNA entry
b) Uptake of naked DNA from environment
c) Fusion of two bacteria
d) Mutation
Answer: b
- b) Correct: Transformation = uptake of naked DNA into bacterial cell.
Q92. The gene gun method is especially useful for:
a) Mammalian cells
b) Plant cells with rigid walls
c) Viruses
d) E. coli
Answer: b
- b) Correct: Biolistics works well in tough plant cells (e.g., maize, rice).
Q93. Which of the following involves direct injection of DNA into the nucleus?
a) Microinjection
b) Electroporation
c) Transformation
d) Biolistics
Answer: a
- a) Correct: Microinjection delivers DNA directly into the nucleus.
Q94. Retroviruses are useful in gene transfer because:
a) They integrate their DNA into host genome
b) They cannot infect humans
c) They only replicate in bacteria
d) They produce antibiotics
Answer: a
- a) Correct: Retroviral vectors integrate stably into host genome.
Q95. Which gene transfer method involves “DNA precipitation on microparticles”?
a) Microinjection
b) Electroporation
c) Biolistics
d) Protoplast fusion
Answer: c
- c) Correct: Biolistics coats DNA onto gold/tungsten microparticles.
Q96. Which method was used to develop Golden Rice?
a) Ti plasmid-mediated transformation
b) Microinjection
c) Gene gun (biolistics)
d) Electroporation
Answer: c
- c) Correct: Golden Rice = produced by gene gun method.
Q97. Competent cells of E. coli can be prepared by:
a) Treating with CaCl₂ followed by heat shock
b) Using streptokinase
c) Adding antibiotics
d) None
Answer: a
- a) Correct: CaCl₂ + heat shock = standard method.
Q98. Which type of transfer uses polyethylene glycol (PEG)?
a) Protoplast fusion
b) Microinjection
c) Viral infection
d) Biolistics
Answer: a
- a) Correct: PEG facilitates protoplast fusion.
Q99. Electroporation is commonly used for:
a) Animal cell transformation
b) Plant cell transformation
c) Bacterial transformation
d) All of the above
Answer: d
- d) Correct: Electroporation works for plants, animals, and bacteria.
Q100. Which statement about gene gun is correct?
a) Uses silver particles
b) Can transfer DNA into both nucleus and chloroplasts
c) Works only in animals
d) Produces blunt ends
Answer: b
- b) Correct: Gene gun DNA can integrate into nucleus and chloroplast genomes.
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