Transformed cell cultures MCQs With Answer provides B. Pharm students a focused revision tool on cell transformation, transfection methods, and stable cell line development. This concise, keyword-rich set covers transfection reagents, viral vectors, selection markers (G418, hygromycin, puromycin), episomal versus integrated DNA, CHO and HEK293 systems, protein expression optimization, biosafety levels, and assay-based screening. Each question emphasizes practical concepts relevant to pharmaceutical research, recombinant protein manufacture, and gene therapy studies. The questions are ideal for exam preparation, viva practice, and laboratory decision-making. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is meant by a “transformed cell culture” in the context of mammalian cells?
- A culture of cells that has been genetically modified to carry new DNA
- A culture of cells grown in transformed glassware
- A culture of cells that has undergone apoptosis
- A culture of cells only derived from bacteria
Correct Answer: A culture of cells that has been genetically modified to carry new DNA
Q2. Which of the following is a common chemical transfection reagent used for mammalian cell transformation?
- Polyethyleneimine (PEI)
- SDS
- Tween 20
- Tris buffer
Correct Answer: Polyethyleneimine (PEI)
Q3. What distinguishes transient transfection from stable transfection?
- Transient uses viral vectors while stable never uses viral vectors
- Transient expression is temporary; stable integrates DNA for long-term expression
- Transient results in permanent genomic integration
- Stable transfection only occurs in bacterial cells
Correct Answer: Transient expression is temporary; stable integrates DNA for long-term expression
Q4. Which cell line is most commonly used for high-yield recombinant protein production in industry?
- CHO (Chinese Hamster Ovary) cells
- E. coli
- Yeast
- HeLa cells
Correct Answer: CHO (Chinese Hamster Ovary) cells
Q5. Which antibiotic is commonly used as a selection marker for the neomycin resistance gene (neo)?
- G418
- Ampicillin
- Chloramphenicol
- Tetracycline
Correct Answer: G418
Q6. What is the primary purpose of a selectable marker in transformed cell cultures?
- To improve cell imaging contrast
- To allow selection of cells that have taken up the transgene
- To change medium pH
- To increase proliferation rate regardless of transformation
Correct Answer: To allow selection of cells that have taken up the transgene
Q7. Which viral vector is known for stable integration into dividing cells and is often used for long-term expression?
- Lentiviral vector
- Adenoviral vector
- Adeno-associated virus (AAV)
- Baculovirus
Correct Answer: Lentiviral vector
Q8. What does MOI (multiplicity of infection) represent in viral transduction?
- The ratio of infectious viral particles to target cells
- The number of plasmids per cell
- The duration of infection in hours
- The fold increase in gene expression
Correct Answer: The ratio of infectious viral particles to target cells
Q9. Which reporter gene is commonly used for real-time fluorescence monitoring of transfection efficiency?
- GFP (Green Fluorescent Protein)
- LacZ
- Chloramphenicol acetyltransferase
- Neomycin phosphotransferase
Correct Answer: GFP (Green Fluorescent Protein)
Q10. Which transfection method uses an electrical pulse to introduce DNA into cells?
- Electroporation
- Lipofection
- Calcium phosphate precipitation
- Microinjection
Correct Answer: Electroporation
Q11. What is a major advantage of using viral vectors over non-viral methods for gene delivery?
- Higher transduction efficiency in many cell types
- Lower biosafety requirements
- No immune response in vivo
- Unlimited insert size capacity
Correct Answer: Higher transduction efficiency in many cell types
Q12. Which promoter is commonly used for strong constitutive expression in mammalian expression vectors?
- CMV (cytomegalovirus) promoter
- T7 promoter
- Lac promoter
- trp promoter
Correct Answer: CMV (cytomegalovirus) promoter
Q13. What is the role of serum in cell culture during transformation experiments?
- Provide growth factors and support cell viability
- Serve as an antibiotic
- Act as a transfection reagent
- Prevent plasmid integration
Correct Answer: Provide growth factors and support cell viability
Q14. Which selection antibiotic is associated with hygromycin resistance genes?
- Hygromycin B
- Puromycin
- Kanamycin
- Streptomycin
Correct Answer: Hygromycin B
Q15. In developing a stable cell line, what is the purpose of single-cell cloning?
- To isolate a monoclonal population with consistent expression
- To increase transfection efficiency
- To remove serum from the culture
- To measure MOI accurately
Correct Answer: To isolate a monoclonal population with consistent expression
Q16. What is an episomal vector?
- A plasmid that replicates independently without integrating into the host genome
- A vector that always integrates into the chromosome
- A virus that cannot infect mammalian cells
- A vector used only in plant cells
Correct Answer: A plasmid that replicates independently without integrating into the host genome
Q17. Which two features are essential in a mammalian expression plasmid?
- Promoter for expression and polyadenylation signal
- Origin of replication from yeast and lac operator
- Ribosome binding site and T7 terminator
- Shine-Dalgarno sequence and oriC
Correct Answer: Promoter for expression and polyadenylation signal
Q18. What is puromycin selection useful for in mammalian cell culture?
- Selecting cells expressing the puromycin-N-acetyltransferase resistance gene
- Promoting viral replication
- Staining cells for microscopy
- Enhancing transfection reagent activity
Correct Answer: Selecting cells expressing the puromycin-N-acetyltransferase resistance gene
Q19. Which assay is commonly used to quantify transient reporter gene expression like luciferase?
- Luminescence assay
- Gram staining
- Western blot
- ELISA for G418
Correct Answer: Luminescence assay
Q20. What is the main biosafety concern when using lentiviral vectors?
- Potential for insertional mutagenesis and handling of replication-competent recombinants
- Large particle size causing clogging
- Inability to transduce non-dividing cells
- Excessive protein expression
Correct Answer: Potential for insertional mutagenesis and handling of replication-competent recombinants
Q21. Which cell property often increases in transformed (immortalized) cell lines compared to primary cells?
- Unlimited proliferative capacity
- Reduced DNA content
- Loss of nucleus
- Inability to adhere to surfaces
Correct Answer: Unlimited proliferative capacity
Q22. What is the function of a signal peptide in recombinant protein production?
- Direct the nascent protein to the secretory pathway for secretion
- Increase plasmid copy number
- Act as a selection marker
- Prevent translation initiation
Correct Answer: Direct the nascent protein to the secretory pathway for secretion
Q23. Which method is suitable for introducing DNA into adherent mammalian cells with low toxicity?
- Lipofection using lipid-based reagents
- Heat shock
- PEG-mediated bacterial transformation
- Glass bead agitation
Correct Answer: Lipofection using lipid-based reagents
Q24. Which component is critical in maintaining plasmid expression in transient transfection experiments?
- High-quality plasmid DNA and optimal transfection reagent ratio
- Antibiotic selection throughout the experiment
- Integrase enzyme in the medium
- Continuous serum starvation
Correct Answer: High-quality plasmid DNA and optimal transfection reagent ratio
Q25. What does “integration site analysis” refer to in stable transformed cell lines?
- Mapping the genomic location where the transgene has integrated
- Measuring plasmid copy number in the cytoplasm
- Analyzing cell membrane composition
- Determining the MOI used
Correct Answer: Mapping the genomic location where the transgene has integrated
Q26. Which of the following increases transformation efficiency during electroporation?
- Optimizing voltage and pulse duration for the specific cell type
- Using cold, ungentle pulses
- Adding RNase to the buffer
- Increasing cell density arbitrarily
Correct Answer: Optimizing voltage and pulse duration for the specific cell type
Q27. For stable expression, why is it important to characterize clonal cell lines over multiple passages?
- To ensure expression stability and rule out silencing or drift
- To check for growth on agar plates
- To induce antibiotic resistance
- To maintain transient expression levels
Correct Answer: To ensure expression stability and rule out silencing or drift
Q28. What is the typical first step after transfection before applying antibiotic selection?
- Allow recovery time for expression of the resistance gene
- Freeze cells immediately
- Add proteases to the culture
- Perform genomic integration PCR
Correct Answer: Allow recovery time for expression of the resistance gene
Q29. Which feature of CHO cells makes them particularly suitable for biopharmaceutical production?
- Human-like glycosylation patterns and regulatory acceptance
- They are prokaryotic and grow very fast
- They lack endoplasmic reticulum
- They always secrete products without signal peptides
Correct Answer: Human-like glycosylation patterns and regulatory acceptance
Q30. What is the role of a reporter gene like luciferase in transformation experiments?
- To provide a measurable signal indicating expression level
- To confer antibiotic resistance
- To integrate plasmid into host genome
- To serve as a promoter
Correct Answer: To provide a measurable signal indicating expression level
Q31. Which factor can lead to transgene silencing in stable mammalian cell lines?
- Integration into heterochromatin regions of the genome
- Using a CMV promoter
- High-copy number plasmids maintained episomally
- Frequent medium changes
Correct Answer: Integration into heterochromatin regions of the genome
Q32. Why is codon optimization done for genes expressed in mammalian transformed cell cultures?
- To match host tRNA abundance and improve translation efficiency
- To make the gene more GC-rich regardless of translation
- To change the protein sequence
- To ensure plasmid integrates into mitochondria
Correct Answer: To match host tRNA abundance and improve translation efficiency
Q33. Which technique is used to confirm presence and correct sequence of an inserted transgene?
- Sanger sequencing of the plasmid or PCR product
- Gram staining
- Protein mass spectrometry only
- ELISA for the selection antibiotic
Correct Answer: Sanger sequencing of the plasmid or PCR product
Q34. In viral vector production, what is “titer”?
- The concentration of infectious viral particles per unit volume
- The total protein content of the viral prep
- The number of antibiotic-resistant colonies
- The pH of the viral suspension
Correct Answer: The concentration of infectious viral particles per unit volume
Q35. Which approach reduces risk of insertional mutagenesis when delivering genes for therapeutic use?
- Using non-integrating vectors like AAV or integrating at safe-harbor sites
- Using higher MOI with lentivirus
- Integrating randomly into oncogenes
- Using plasmids without promoters
Correct Answer: Using non-integrating vectors like AAV or integrating at safe-harbor sites
Q36. What is the significance of serum-free media for production cell lines?
- Improves downstream purification and reduces variability and risk of contaminants
- Prevents any protein secretion
- Kills all non-transformed cells
- Increases genomic integration events
Correct Answer: Improves downstream purification and reduces variability and risk of contaminants
Q37. How is transfection efficiency commonly quantified in a cell population?
- Flow cytometry for fluorescent reporters like GFP
- Measuring absorbance at 260 nm
- Counting colony-forming units on agar
- Gram staining
Correct Answer: Flow cytometry for fluorescent reporters like GFP
Q38. What does “bicistronic vector” typically contain?
- Two open reading frames enabling co-expression of two genes
- A single gene with two promoters for the same protein
- A vector for bacteria and yeast simultaneously
- Only regulatory sequences but no coding regions
Correct Answer: Two open reading frames enabling co-expression of two genes
Q39. Which analytical method is best to assess correct folding and glycosylation of a secreted recombinant protein?
- Mass spectrometry and glycan analysis
- PCR for the transgene
- Antibiotic sensitivity test
- UV absorbance at 280 nm alone
Correct Answer: Mass spectrometry and glycan analysis
Q40. During stable cell line development, what does “pool” refer to?
- A mixed population of antibiotic-resistant cells prior to cloning
- A culture of only bacteria
- A single clone isolated by limiting dilution
- A water bath used for heat shock
Correct Answer: A mixed population of antibiotic-resistant cells prior to cloning
Q41. Which factor enhances secretion of recombinant proteins from mammalian cells?
- Inclusion of an appropriate signal peptide and optimizing ER capacity
- Removing the polyadenylation signal
- Using prokaryotic promoters
- Keeping cells at very low temperature always
Correct Answer: Inclusion of an appropriate signal peptide and optimizing ER capacity
Q42. What is “antibiotic selection pressure” in the context of transformed cultures?
- Continuous presence of antibiotic to maintain only resistant, transgene-carrying cells
- Reducing antibiotic to zero to improve expression
- Using antibiotics to stimulate transcription
- Testing bacterial contamination only
Correct Answer: Continuous presence of antibiotic to maintain only resistant, transgene-carrying cells
Q43. Which of these is a non-viral physical transfection technique suitable for hard-to-transfect cells?
- Nucleofection
- Calcium-free media
- Lactase treatment
- Conjugation with plasmid-binding proteins
Correct Answer: Nucleofection
Q44. What is an advantage of using HEK293 cells for transient protein expression?
- High transfection efficiency and rapid protein production
- They always glycosylate proteins identically to humans
- They are antibiotic-resistant by default
- They never require serum
Correct Answer: High transfection efficiency and rapid protein production
Q45. Which component of an expression cassette prevents premature transcription termination in eukaryotes?
- Polyadenylation signal and transcriptional terminator elements
- Ribosome binding site
- Origin of replication
- Selectable marker gene
Correct Answer: Polyadenylation signal and transcriptional terminator elements
Q46. Why might one use inducible expression systems in transformed cell cultures?
- To control timing and level of transgene expression and reduce toxicity
- To permanently silence the gene
- To avoid using any selection markers
- To ensure constitutive overexpression regardless of conditions
Correct Answer: To control timing and level of transgene expression and reduce toxicity
Q47. Which quality attribute is critical for therapeutic proteins produced in transformed mammalian cells?
- Proper glycosylation and correct folding
- Presence of bacterial endotoxin only
- High DNA contamination in final product
- Random proteolytic fragments intentionally included
Correct Answer: Proper glycosylation and correct folding
Q48. What is the purpose of using flow cytometry during selection of transformed cell lines?
- To sort and analyze cells based on fluorescent reporter expression or surface markers
- To measure antibiotic concentration
- To quantify plasmid DNA in solution
- To visually inspect colonies under a microscope
Correct Answer: To sort and analyze cells based on fluorescent reporter expression or surface markers
Q49. How can off-target effects of genome editing in transformed cultures be minimized?
- Designing specific guide RNAs and validating edits by sequencing
- Using very high concentrations of nuclease without controls
- Avoiding sequencing after editing
- Only using plasmids without guides
Correct Answer: Designing specific guide RNAs and validating edits by sequencing
Q50. Which regulatory consideration is most important when producing recombinant therapeutics in transformed cell cultures?
- Ensuring product safety, purity, consistent glycosylation, and compliance with GMP
- Maximizing antibiotic concentration in final drug formulation
- Using uncharacterized cell banks to save cost
- Skipping validation to accelerate release
Correct Answer: Ensuring product safety, purity, consistent glycosylation, and compliance with GMP
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