Golden Rice, developed through genetic engineering, is primarily enriched with which nutrient?

The correct answer is B: Beta-carotene (Vitamin A precursor). Golden Rice contains beta-carotene, a precursor to Vitamin A, which is added to combat Vitamin A deficiency in developing countries. It was developed using genes from daffodil and bacterium Erwinia uredovora.

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

The correct answer is A: Flask → 10L bioreactor → 100L bioreactor → 1000L bioreactor. 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.

What is the primary mechanism by which RNA interference (RNAi) achieves gene silencing?

The correct answer is A: Degradation of the target mRNA by siRNA-guided enzymes. RNAi uses small interfering RNAs (siRNAs) that guide the RNA-Induced Silencing Complex (RISC) to degrade specific target mRNAs, effectively silencing gene expression post-transcriptionally.

In RAPD-PCR (Random Amplified Polymorphic DNA), what is the primary application in agricultural biotechnology?

The correct answer is A: Genetic fingerprinting and diversity analysis. RAPD-PCR uses random primers to generate DNA fingerprints for assessing genetic diversity, distinguishing crop varieties, and parentage analysis in breeding programs.

In a typical PCR cycle, DNA denaturation occurs at approximately which temperature?

The correct answer is B: 94-95°C. DNA denaturation in PCR occurs at 94-95°C (or sometimes 98°C), where hydrogen bonds between DNA strands are broken, separating the double helix into single strands.

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Biotechnology
PCR & DNA Technology

Genetic engineering, fermentation, cell biology

100 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 100

Topics in Biotechnology

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

Q.1 Medium PCR & DNA Technology

In a multiplex PCR assay designed to simultaneously amplify 6 different STR (short tandem repeat) loci for forensic DNA profiling, what is the critical consideration that must be addressed?

A All primers must have identical Tm values and amplicons of similar sizes to avoid preferential amplification

B Each primer pair must amplify loci on different chromosomes

C The assay must include at least two internal positive controls

D All amplicons must be shorter than 200 bp

Correct Answer: A. All primers must have identical Tm values and amplicons of similar sizes to avoid preferential amplification

EXPLANATION

In multiplex PCR, primers with similar Tm values ensure equal amplification efficiency across all targets. Amplicons of comparable sizes prevent preferential amplification of shorter fragments (which amplify faster), ensuring balanced and accurate STR profiles for individual identification.

Test

Q.2 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.3 Medium PCR & DNA Technology

During PCR amplification, the annealing temperature is set based on the Tm (melting temperature) of primers. If primers with Tm of 58°C and 62°C are used in the same reaction, what would be the optimal annealing temperature to ensure efficient amplification of both targets?

A 62°C

B 58°C

C 60°C

D 55°C

Correct Answer: B. 58°C

EXPLANATION

The optimal annealing temperature should be set at or slightly below the Tm of the primer with the lowest Tm (58°C) to prevent primer dissociation while maintaining specificity. Using 58°C ensures both primers can bind efficiently.

Test

Q.4 Medium PCR & DNA Technology

In next-generation sequencing library preparation, why is PCR amplification of adaptor-ligated DNA fragments critical?

A To purify DNA from contaminating proteins

B To enrich specific genomic regions of interest

C To amplify low-quantity samples to sufficient DNA amount for sequencing and add sequencing indices

D To eliminate GC-rich regions

Correct Answer: C. To amplify low-quantity samples to sufficient DNA amount for sequencing and add sequencing indices

EXPLANATION

NGS requires substantial DNA; PCR amplifies adaptor-ligated fragments while incorporating index sequences for multiplexing, enabling efficient library preparation.

Test

Q.5 Easy PCR & DNA Technology

What is the primary role of dNTPs (deoxynucleotide triphosphates) in the PCR reaction mixture?

A To serve as substrates for DNA polymerase extension

B To activate Taq polymerase

C To maintain pH of the buffer

D To provide energy for primer denaturation

Correct Answer: A. To serve as substrates for DNA polymerase extension

EXPLANATION

dNTPs (dATP, dGTP, dCTP, dTTP) are incorporated into the growing DNA strand by Taq polymerase via phosphodiester bond formation.

Test

Q.6 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.7 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.8 Medium PCR & DNA Technology

In the context of environmental microbiology, what does PCR-DGGE (Denaturing Gradient Gel Electrophoresis) primarily assess?

A Absolute bacterial population size

B Microbial community composition and diversity without requiring cultivation

C Antibiotic resistance genes only

D Heavy metal accumulation in bacteria

Correct Answer: B. Microbial community composition and diversity without requiring cultivation

EXPLANATION

PCR-DGGE separates PCR amplicons based on melting behavior, providing a fingerprint of microbial community structure independent of culture.

Test

Q.9 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.10 Medium PCR & DNA Technology

In homozygous versus heterozygous allele detection using allele-specific PCR, which outcome indicates a heterozygous genotype?

A Amplification with both allele-specific primers in separate reactions

B No amplification in either reaction

C Amplification with only one allele-specific primer

D Amplification occurs at lower temperatures

Correct Answer: A. Amplification with both allele-specific primers in separate reactions

EXPLANATION

Heterozygotes carry both alleles; separate allele-specific primer sets each amplify their respective allele, showing amplification in both reactions.

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