Strain improvement techniques MCQs With Answer

Introduction: Strain improvement techniques MCQs With Answer is designed for M.Pharm students specializing in bioprocess engineering and biotechnology. This blog offers focused multiple-choice questions that cover classical and modern methods used to enhance microbial and cell-line performance for industrial bioproduction. Topics include mutagenesis, recombination, protoplast fusion, adaptive laboratory evolution, genome shuffling, metabolic and regulatory engineering, CRISPR-mediated editing, and strategies for screening, selection and stability. Each question emphasizes practical applications, mechanism understanding and decision-making in strain development for pharmaceutical bioprocesses. Use these MCQs for revision, exam preparation and to deepen conceptual knowledge on optimizing strains for yield, productivity and robustness.

Q1. Which strain improvement technique relies on repeated rounds of random mutagenesis followed by recombination of improved populations to accelerate accumulation of beneficial mutations?

• Directed evolution by site-directed mutagenesis
• Genome shuffling
• Protoplast fusion without selection
• Adaptive laboratory evolution under constant conditions

Correct Answer: Genome shuffling

Q2. Which mutagen is most likely to cause transitions by alkylating guanine to pair with thymine, leading to GC→AT mutations?

• Ethyl methane sulfonate (EMS)
• Ultraviolet (UV) radiation
• Nitrosoguanidine (NTG)
• Gamma radiation

Correct Answer: Ethyl methane sulfonate (EMS)

Q3. In protoplast fusion for strain improvement, what is the primary advantage of using PEG (polyethylene glycol)?

• PEG acts as a selective marker for fusants
• PEG facilitates cell wall degradation
• PEG promotes membrane fusion between protoplasts
• PEG increases mutation rate in fused cells

Correct Answer: PEG promotes membrane fusion between protoplasts

Q4. Which screening strategy is most appropriate when the desired trait is increased secretion of a pharmaceutical enzyme?

• Auxotrophic selection on minimal media
• High-throughput plate assay measuring secreted enzyme activity
• Antibiotic resistance screening
• Screening for colony morphology changes

Correct Answer: High-throughput plate assay measuring secreted enzyme activity

Q5. Adaptive laboratory evolution (ALE) primarily selects for which of the following?

• Directed single-nucleotide changes at target loci
• Phenotypes that confer growth advantage under defined stress or conditions
• Horizontal gene transfer events only
• Increased plasmid copy number independent of selection pressure

Correct Answer: Phenotypes that confer growth advantage under defined stress or conditions

Q6. Which genetic engineering approach allows precise, targeted changes to increase production of a metabolic intermediate by knocking out competing pathways?

• Random chemical mutagenesis
• CRISPR-Cas9 mediated gene knockout
• Protoplast fusion
• Genome shuffling

Correct Answer: CRISPR-Cas9 mediated gene knockout

Q7. Ribosome engineering enhances secondary metabolite production by selecting mutations in ribosomal proteins or RNA that affect which cellular process?

• Cell wall biosynthesis
• Transcription and translational fidelity, altering global regulation
• DNA replication origin usage
• Mitochondrial respiration exclusively

Correct Answer: Transcription and translational fidelity, altering global regulation

Q8. Which of the following best describes the role of reporter genes (e.g., GFP, lacZ) in high-throughput strain improvement?

• Reporter genes directly increase product yield
• Reporters enable rapid identification of clones with desired promoter activity or secretion
• Reporters serve as selectable antibiotics
• Reporter genes are used to increase mutation rates

Correct Answer: Reporters enable rapid identification of clones with desired promoter activity or secretion

Q9. Which physical mutagen primarily causes formation of thymine dimers and is commonly used for generating point mutations in microbial genomes?

• Gamma radiation
• Ultraviolet (UV) radiation
• X-rays
• Sonication

Correct Answer: Ultraviolet (UV) radiation

Q10. When improving production strains, why is stability testing of the phenotype important during scale-up?

• Stability testing is only necessary for academic studies
• To ensure the improved trait is maintained over multiple generations and under industrial conditions
• Because genetics never changes during fermentation
• To intentionally select for loss of plasmids

Correct Answer: To ensure the improved trait is maintained over multiple generations and under industrial conditions

Q11. Which selection marker strategy is used to maintain plasmids in production strains without antibiotics and relies on complementation of an essential gene?

• Antibiotic resistance marker maintenance
• Auxotrophic complementation
• GFP fluorescence selection
• Counter-selection using sacB

Correct Answer: Auxotrophic complementation

Q12. Genome-scale metabolic engineering for strain improvement often uses which computational technique to predict gene targets for enhanced metabolite production?

• Random forest classification without biochemical constraints
• Flux balance analysis (FBA)
• Principal component analysis of raw sequence reads
• BLAST homology search only

Correct Answer: Flux balance analysis (FBA)

Q13. Directed evolution for enzyme improvement typically involves iterative cycles of mutagenesis and:

• Protoplast fusion
• Screening or selection for improved function
• Genome shuffling without screening
• CRISPR-based multiplexed editing

Correct Answer: Screening or selection for improved function

Q14. Which approach combines rational design and random mutagenesis by targeting mutagenesis to specific protein regions important for activity?

• Genome shuffling
• Site-saturation mutagenesis
• Whole-genome resequencing
• Adaptive laboratory evolution only

Correct Answer: Site-saturation mutagenesis

Q15. Metabolic burden in engineered strains often arises from high-level expression of heterologous pathways. Which strategy can reduce burden while maintaining product titer?

• Increase plasmid copy number indefinitely
• Chromosomal integration of pathway genes and regulated promoters
• Remove all feedback regulation in central metabolism
• Apply continuous high-dose antibiotics

Correct Answer: Chromosomal integration of pathway genes and regulated promoters

Q16. Which selection method exploits the requirement of a product or intermediate for growth, enabling enrichment of producers in a mixed population?

• Phenotypic microarray screening
• Product-dependent growth selection (metabolite auxotrophy complementation)
• Colony PCR screening of random clones
• Visual colony color screening only

Correct Answer: Product-dependent growth selection (metabolite auxotrophy complementation)

Q17. In microbial strain improvement, what advantage does multiplex automated genome engineering (MAGE) provide?

• It randomly shuffles entire genomes without design
• Enables simultaneous targeted modifications at many loci to explore combinatorial genotypes
• Is limited to editing a single gene at a time
• Relies exclusively on natural horizontal gene transfer

Correct Answer: Enables simultaneous targeted modifications at many loci to explore combinatorial genotypes

Q18. Which screening technology allows sorting of millions of cells per hour based on secreted product linked to a fluorescent reporter in microdroplets?

• Conventional microplate assay
• Fluorescence-activated droplet sorting (FADS)
• Low-throughput shake flask screening
• Serial dilution plating

Correct Answer: Fluorescence-activated droplet sorting (FADS)

Q19. Which effect is a common unintended consequence of strong promoter overexpression of pathway enzymes in production strains?

• Improved folding and no stress response
• Formation of inclusion bodies, metabolic imbalance and increased burden
• Guaranteed proportional increase in product yield without trade-offs
• Complete shutdown of central carbon metabolism without any rescue

Correct Answer: Formation of inclusion bodies, metabolic imbalance and increased burden

Q20. When using classical mutagenesis followed by selection, why is it important to combine phenotype screening with genotypic characterization of selected strains?

• Because phenotype alone guarantees pathway knowledge
• To understand the genetic basis of improvement, ensure stability, and avoid deleterious off-target mutations
• Genotypic data is irrelevant for industrial strains
• Screening is sufficient; genotyping only adds cost without benefit

Correct Answer: To understand the genetic basis of improvement, ensure stability, and avoid deleterious off-target mutations

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