Which gas composition is typically maintained in mammalian cell culture bioreactors?

The correct answer is B: 5% CO2, 5% O2, 90% N2. 5% CO2 maintains pH through bicarbonate buffering, 5% O2 provides aerobic respiration, and N2 balances the gas mixture. This mimics physiological conditions.

Which of the following statements about lactate production in mammalian cell culture is correct?

The correct answer is B: Lactate is a waste product that accumulates and inhibits cell growth at high concentrations. Lactate accumulates as a metabolic byproduct and at concentrations >15-20 mM can inhibit cell growth and reduce productivity. Lactate management is crucial in fed-batch cultures.

In a perfusion bioreactor system used for continuous cell culture, what is the primary advantage over batch culture?

The correct answer is B: It removes waste products and replenishes nutrients continuously, allowing prolonged culture and higher cell densities. Perfusion systems continuously exchange medium, removing metabolic wastes and supplying nutrients, enabling higher cell densities and prolonged culture periods compared to batch systems.

In CRISPR-Cas9 technology, what is the function of the guide RNA (gRNA)?

The correct answer is B: To direct Cas9 protein to the target DNA sequence. The guide RNA is complementary to the target DNA sequence and directs the Cas9 nuclease to the correct location for DNA cleavage.

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Biotechnology
PCR & DNA Technology

Genetic engineering, fermentation, cell biology

28 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 28

Topics in Biotechnology

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

Q.1 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.2 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.3 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.4 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.5 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

Q.6 Hard PCR & DNA Technology

Which DNA technology would be most appropriate for detecting point mutations and SNPs in cancer genomics?

A RFLP analysis

B DGGE (Denaturing Gradient Gel Electrophoresis)

C Next-generation sequencing (NGS) or digital PCR with allele-specific primers

D Standard PCR followed by agarose gel electrophoresis

Correct Answer: C. Next-generation sequencing (NGS) or digital PCR with allele-specific primers

EXPLANATION

NGS and allele-specific digital PCR can detect rare mutations (ctDNA) with high sensitivity; RFLP/DGGE are less sensitive for point mutation detection.

Test

Q.7 Hard PCR & DNA Technology

In droplet digital PCR (ddPCR), the sample is partitioned into thousands of micro-compartments. What is the primary advantage of this approach?

A Increases annealing temperature specificity

B Enables absolute quantification without standard curves

C Reduces primer dimer formation

D Eliminates the need for thermal cycling

Correct Answer: B. Enables absolute quantification without standard curves

EXPLANATION

ddPCR partitions samples into independent reactions, allowing Poisson distribution analysis for absolute quantification without reference standards.

Test

Q.8 Hard PCR & DNA Technology

Which DNA amplification technique is used to amplify sequences adjacent to a known sequence boundary?

A Standard PCR

B Inverse PCR

C Linear amplification

D Strand displacement amplification

Correct Answer: B. Inverse PCR

EXPLANATION

Inverse PCR amplifies unknown DNA sequences flanking a known region by using outward-facing primers on a circularized DNA template, useful for genome walking and transposon mapping.

Test

Q.9 Hard PCR & DNA Technology

In SNP genotyping using TaqMan chemistry, what is the function of MGB (Minor Groove Binder)?

A To increase the denaturation temperature

B To enhance probe specificity and increase Tm without lengthening the probe

C To serve as the fluorescent reporter dye

D To reduce primer-dimer formation

Correct Answer: B. To enhance probe specificity and increase Tm without lengthening the probe

EXPLANATION

MGB sequences bind in the minor groove of DNA, stabilizing the probe-DNA duplex and increasing its melting temperature, allowing for shorter, more specific probes.

Test

Q.10 Hard PCR & DNA Technology

In the context of DNA barcoding for species identification, which gene region is commonly used for plants?

A 16S rRNA

B rbcL and matK

C cytochrome c oxidase I (COI)

D 18S rRNA

Correct Answer: B. rbcL and matK

EXPLANATION

For plant DNA barcoding, rbcL (ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit) and matK (maturase K) are the standard barcode regions recognized by CBOL.

Test

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