Which of the following best describes the G0 phase in the cell cycle?

The correct answer is C: Quiescent/resting phase where cells exit active division. G0 (G-zero) represents the quiescent state where cells are metabolically active but not dividing. Cells can exit G1 phase and enter G0 under nutrient limitation or other stress conditions.

Which hormone is most critical for cell growth and proliferation in serum-containing culture media?

The correct answer is C: Growth factors present in serum (FBS). Fetal Bovine Serum (FBS) contains essential growth factors, hormones, and attachment factors that promote cell growth and proliferation in culture.

What is the primary advantage of using viral vectors in gene therapy?

The correct answer is B: They have evolved mechanisms to deliver DNA efficiently into cells. Viruses have naturally evolved sophisticated mechanisms to infiltrate cells and deliver their genetic material, making modified viral vectors efficient delivery systems for therapeutic genes.

What is the primary function of osmolarity/osmotic pressure control in cell culture media?

The correct answer is B: To maintain cell volume and prevent lysis or crenation. Proper osmolarity (typically 280-320 mOsm/kg) maintains isotonic conditions, preventing cell swelling (hypotonic) or shrinkage (hypertonic), which would lead to cell damage.

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Biotechnology

Genetic engineering, fermentation, cell biology

67 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 67

Topics in Biotechnology

All Genetic Engineering 100 PCR & DNA Technology 100 Cell Culture 60

Q.11 Hard Cell Culture

What is the significance of mycoplasma testing in cell culture quality control for biopharmaceutical production?

A Mycoplasma detection is optional and rarely performed

B Mycoplasma contamination is easily visible under light microscope

C Mycoplasma is a critical contaminant that requires detection by PCR or ELISA to ensure product safety and efficacy

D Mycoplasma only affects bacterial cultures, not mammalian cells

Correct Answer: C. Mycoplasma is a critical contaminant that requires detection by PCR or ELISA to ensure product safety and efficacy

EXPLANATION

Mycoplasma is an obligatory contaminant in cell cultures that can affect cell behavior and product quality. Detection via PCR, culture, or ELISA is mandatory in biopharmaceutical manufacturing per ICH guidelines.

Test

Q.12 Hard Cell Culture

Which of the following represents the correct sequence in scaling up cell culture from laboratory to industrial bioreactor?

A Flask → 10L bioreactor → 100L bioreactor → 1000L bioreactor

B 1000L bioreactor → 100L bioreactor → 10L bioreactor → Flask

C 10L bioreactor → Flask → 100L bioreactor → 1000L bioreactor

D All scales can be done simultaneously without sequence

Correct Answer: A. Flask → 10L bioreactor → 100L bioreactor → 1000L bioreactor

EXPLANATION

Scale-up follows a logical progression from small (flask) to larger volumes, with each step validated for maintaining cell viability, growth rate, and product quality.

Test

Q.13 Hard Cell Culture

In the context of vaccine production using cell culture, which cell lines are most commonly used in India?

A Only bacterial cultures

B Vero cells, CHO cells, and HEK293 cells

C Fungal cultures exclusively

D Plant callus tissues only

Correct Answer: B. Vero cells, CHO cells, and HEK293 cells

EXPLANATION

Vero (monkey kidney), CHO (hamster ovary), and HEK293 (human embryonic kidney) cells are widely used for vaccine production including COVID-19 and other vaccines in India.

Test

Q.14 Hard Cell Culture

A researcher observes that their CHO (Chinese Hamster Ovary) cell culture shows reduced protein production despite maintaining normal cell density. What could be the most likely cause?

A Excessive CO₂ concentration above 10%

B Suboptimal osmolarity or nutrient depletion in the medium

C Temperature too high (above 40°C)

D Presence of antibiotics in the medium

Correct Answer: B. Suboptimal osmolarity or nutrient depletion in the medium

EXPLANATION

Even at normal density, cells require optimal osmolarity (280-320 mOsm/kg) and adequate nutrients. Nutrient depletion reduces metabolic activity and protein synthesis despite maintained cell count.

Test

Q.15 Hard Cell Culture

What is the primary limitation of primary cell cultures compared to continuous cell lines?

A They are more expensive to establish initially

B They have limited lifespan and gradually lose original characteristics

C They cannot be used for any research purpose

D They grow faster than continuous cell lines

Correct Answer: B. They have limited lifespan and gradually lose original characteristics

EXPLANATION

Primary cells have limited replicative lifespan due to the Hayflick limit and may undergo changes over passages, whereas continuous cell lines can divide indefinitely.

Test

Q.16 Hard PCR & DNA Technology

A researcher is performing digital PCR (dPCR) for absolute quantification of mutant KRAS alleles in circulating tumor DNA (ctDNA). Compared to conventional qPCR, what is the primary advantage of dPCR in this application?

A It requires fewer PCR cycles for amplification

B It provides absolute quantification independent of standard curves and is more sensitive for rare mutations in low-frequency alleles

C It eliminates the need for fluorescent probes

D It allows amplification of longer DNA fragments (>5 kb)

Correct Answer: B. It provides absolute quantification independent of standard curves and is more sensitive for rare mutations in low-frequency alleles

EXPLANATION

Digital PCR partitions samples into thousands of individual reactions, enabling absolute quantification without standard curves. This is crucial for detecting rare mutations where ctDNA comprises only 0.01-1% of total circulating DNA, making it superior for cancer diagnostics.

Test

Q.17 Hard PCR & DNA Technology

In the amplification of GC-rich genomic regions, which strategy is most effective to reduce secondary structure formation?

A Decrease magnesium chloride concentration

B Use of DMSO or betaine, increase denaturation temperature, and employ high-fidelity polymerases

C Reduce primer annealing temperature

D Increase the number of PCR cycles

Correct Answer: B. Use of DMSO or betaine, increase denaturation temperature, and employ high-fidelity polymerases

EXPLANATION

GC-rich regions form hairpins; additives (DMSO/betaine) destabilize secondary structures, while higher denaturation temperatures and specialized polymerases enhance amplification.

Test

Q.18 Hard PCR & DNA Technology

Which PCR-based technique would be most suitable for detecting mutations associated with antibiotic resistance in Mycobacterium tuberculosis in clinical samples?

A RAPD-PCR

B Mutation-specific PCR or allele-specific qPCR targeting known resistance-conferring mutations

C RFLP followed by Southern blotting

D Standard PCR with agarose gel analysis

Correct Answer: B. Mutation-specific PCR or allele-specific qPCR targeting known resistance-conferring mutations

EXPLANATION

Allele-specific qPCR can rapidly detect known resistance mutations (e.g., rpoB in rifampicin resistance) in clinical TB samples for faster diagnosis.

Test

Q.19 Hard PCR & DNA Technology

Which modification to standard PCR allows amplification of extremely long DNA fragments (>3 kb)?

A Increasing denaturation temperature

B Using high-fidelity polymerase with proofreading activity and optimized buffer conditions

C Reducing primer annealing temperature

D Shortening elongation time

Correct Answer: B. Using high-fidelity polymerase with proofreading activity and optimized buffer conditions

EXPLANATION

Long-range PCR requires thermostable polymerases with 3'→5' exonuclease activity (e.g., Pfu, Phusion) and extended elongation times for processivity.

Test

Q.20 Hard PCR & DNA Technology

What is the primary challenge in developing universal primers for metagenomic studies of microbial communities?

A High cost of oligonucleotide synthesis

B Sequence heterogeneity among different microbial species requires balancing sensitivity and specificity

C Inability of Taq polymerase to amplify GC-rich regions

D Unavailability of appropriate restriction enzymes

Correct Answer: B. Sequence heterogeneity among different microbial species requires balancing sensitivity and specificity

EXPLANATION

Universal primers (e.g., 16S rRNA) must accommodate sequence variations across taxa while maintaining specificity, creating a design dilemma.

Test

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