What is the significance of using antifoam agents in large-scale bioreactors?

The correct answer is B: To prevent foam formation which can cause cell damage and overflow. Foam formation in bioreactors during aeration can cause cell lysis, loss of surface area, and carryover into exhaust lines. Antifoam agents (silicone-based) prevent this.

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 significance of cryopreservation in cell culture banking?

The correct answer is B: It maintains cell viability and genetic integrity for long-term storage. Cryopreservation using liquid nitrogen or cryoprotectants like DMSO allows cells to be stored long-term while maintaining viability and genetic stability for future use.

Which annealing temperature is most appropriate for primers with a GC content of 50%?

The correct answer is B: 55-60°C. Annealing temperature is typically 3-5°C below the Tm (melting temperature). For 50% GC content, Tm ≈ 55-60°C, making this the appropriate annealing range.

What is the primary limitation of PCR when amplifying GC-rich sequences?

The correct answer is B: Secondary structures form, reducing amplification efficiency. GC-rich sequences tend to form stable secondary structures (hairpins, loops), which can inhibit primer annealing and polymerase extension, reducing PCR efficiency.

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Biotechnology

Genetic engineering, fermentation, cell biology

67 Q 3 Topics Take Mock Test

Difficulty: All Easy Medium Hard 41–50 of 67

Topics in Biotechnology

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

Q.41 Hard PCR & DNA Technology

In gene editing, CRISPR-Cas9 uses which type of guide molecule?

A Single-stranded DNA (ssDNA)

B Guide RNA (sgRNA)

C Protein only

D Restriction enzyme

Correct Answer: B. Guide RNA (sgRNA)

EXPLANATION

CRISPR-Cas9 employs a single guide RNA (sgRNA) that directs Cas9 endonuclease to specific DNA target sequences for precise editing.

Test

Q.42 Hard PCR & DNA Technology

The principle of AFLP (Amplified Fragment Length Polymorphism) combines:

A Restriction digestion and PCR amplification

B Southern blotting and sequencing

C RFLP and DNA fingerprinting only

D Gel electrophoresis and RAPD

Correct Answer: A. Restriction digestion and PCR amplification

EXPLANATION

AFLP integrates restriction enzyme digestion with selective PCR amplification of restriction fragments for genetic diversity analysis.

Test

Q.43 Hard PCR & DNA Technology

In cloning, which vector is most suitable for inserting large DNA fragments (>15 kb)?

A Plasmid vectors

B Cosmid vectors

C Phage vectors

D Phagemid vectors

Correct Answer: B. Cosmid vectors

EXPLANATION

Cosmids can accommodate DNA inserts of 35-45 kb, making them ideal for large DNA fragments compared to plasmids (5-20 kb).

Test

Q.44 Hard Genetic Engineering

Which of the following represents a limitation of homologous recombination-based gene targeting?

A Very high efficiency in mammalian cells without selection

B Low frequency of homologous recombination in mammalian somatic cells (~1 in 10^6-10^7)

C Inability to create specific mutations

D High off-target effects

Correct Answer: B. Low frequency of homologous recombination in mammalian somatic cells (~1 in 10^6-10^7)

EXPLANATION

Homologous recombination has very low frequency in mammalian cells compared to yeast, requiring enrichment strategies and selection markers. This limitation has been overcome by CRISPR technology.

Test

Q.45 Hard Genetic Engineering

In next-generation sequencing (NGS), what is the primary advantage of whole-genome sequencing over targeted gene sequencing?

A Lower cost per base

B Detection of unknown mutations and structural variations across the entire genome

C Faster processing time

D Higher accuracy for specific genes

Correct Answer: B. Detection of unknown mutations and structural variations across the entire genome

EXPLANATION

Whole-genome sequencing provides unbiased coverage of the entire genome, allowing discovery of unexpected mutations, copy number variations, and structural rearrangements not detected by targeted approaches.

Test

Q.46 Hard Genetic Engineering

What is the primary mechanism of action of TALENs (Transcription Activator-Like Effector Nucleases) in gene editing?

A Formation of secondary structures to block transcription

B Modular DNA-binding domain directs FokI nuclease to specific target sequences

C Competitive inhibition of RNA polymerase

D Methylation of target DNA

Correct Answer: B. Modular DNA-binding domain directs FokI nuclease to specific target sequences

EXPLANATION

TALENs consist of a modular DNA-binding domain (which recognizes specific sequences) fused to the FokI nuclease domain, allowing precise DNA cleavage at target sites.

Test

Q.47 Hard Genetic Engineering

Which epigenetic modification is commonly exploited in epigenome editing to achieve stable gene silencing without altering DNA sequence?

A Histone acetylation

B DNA methylation and histone deacetylation using dCas9-KRAB fusion proteins

C Phosphorylation of histone tails

D Ubiquitination of DNA-binding proteins

Correct Answer: B. DNA methylation and histone deacetylation using dCas9-KRAB fusion proteins

EXPLANATION

dCas9-KRAB recruits repressor complexes causing DNA methylation and histone deacetylation, establishing stable heterochromatin without genetic changes, useful for therapeutic gene silencing.

Test

Q.48 Hard Genetic Engineering

In base editing technology, what is the critical difference between cytidine and adenosine deaminases in terms of target DNA modification?

A Both convert identical nucleotides

B Cytidine deaminases convert C-G to T-A; adenosine deaminases convert A-T to G-C

C Adenosine deaminases are more efficient

D Cytidine deaminases require guide RNAs while adenosine don't

Correct Answer: B. Cytidine deaminases convert C-G to T-A; adenosine deaminases convert A-T to G-C

EXPLANATION

Cytidine deaminase (APOBEC) converts cytosine to uracil (paired with G) leading to C-G→T-A transition. TadA adenosine deaminase converts adenosine to inosine (read as G), causing A-T→G-C.

Test

Q.49 Hard Genetic Engineering

Which technique combines microfluidics with next-generation sequencing to analyze single-cell genetic modifications in heterogeneous populations?

A Bulk RNA-seq

B Digital droplet PCR

C Single-cell CRISPR screening (scCRISPR-seq)

D Array comparative genomic hybridization

Correct Answer: C. Single-cell CRISPR screening (scCRISPR-seq)

EXPLANATION

scCRISPR-seq enables simultaneous analysis of CRISPR perturbations and transcriptome responses at single-cell level, revealing cellular heterogeneity in gene-edited populations.

Test

Q.50 Hard Genetic Engineering

In the context of gene therapy vectors, which characteristic makes adeno-associated viruses (AAVs) preferable to lentiviruses for CNS diseases?

A Larger packaging capacity

B Ability to integrate into genome

C Smaller size allowing better blood-brain barrier penetration and lower immunogenicity

D Higher transduction efficiency in non-dividing cells

Correct Answer: C. Smaller size allowing better blood-brain barrier penetration and lower immunogenicity

EXPLANATION

AAVs are 25 nm particles with limited packaging (~4.7 kb) but excellent CNS tropism, low immunogenicity, and non-integrating nature, making them safer for neurological applications.

Test

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