Q.1 What does the abbreviation ‘rDNA’ stand for in biotechnology?
Random DNA
Recombinant DNA
Reverse DNA
Regulated DNA
Explanation - rDNA refers to DNA molecules that have been formed by combining genetic material from multiple sources, creating a new sequence not found in nature.
Correct answer is: Recombinant DNA
Q.2 Which enzyme is primarily used to cut DNA at specific sequences during recombinant DNA experiments?
DNA polymerase
RNA ligase
Restriction endonuclease
Helicase
Explanation - Restriction endonucleases recognize specific palindromic sequences and cleave the DNA at or near these sites, enabling precise DNA manipulation.
Correct answer is: Restriction endonuclease
Q.3 In a plasmid vector, the origin of replication (ori) is essential because it:
Encodes a selectable marker
Allows the plasmid to replicate independently in the host cell
Provides a site for DNA insertion
Regulates transcription of inserted genes
Explanation - The ori is a DNA sequence that signals the host’s replication machinery to duplicate the plasmid, ensuring its maintenance in daughter cells.
Correct answer is: Allows the plasmid to replicate independently in the host cell
Q.4 Which of the following is a common selectable marker used in bacterial cloning vectors?
Green fluorescent protein (GFP)
Beta-galactosidase (lacZ)
Ampicillin resistance gene (bla)
Tetracycline repressor (tetR)
Explanation - The bla gene confers resistance to ampicillin, allowing only bacteria that have taken up the plasmid to grow on antibiotic-containing media.
Correct answer is: Ampicillin resistance gene (bla)
Q.5 What is the purpose of a multiple cloning site (MCS) in a plasmid vector?
To increase plasmid copy number
To provide a region with many restriction sites for easy insertion of DNA fragments
To encode a fluorescent reporter gene
To control plasmid stability
Explanation - An MCS contains several unique restriction sites, facilitating the insertion of DNA fragments using various enzymes.
Correct answer is: To provide a region with many restriction sites for easy insertion of DNA fragments
Q.6 Which host organism is most commonly used for cloning recombinant DNA for protein production?
Saccharomyces cerevisiae
Escherichia coli
Bacillus subtilis
Arabidopsis thaliana
Explanation - E. coli grows rapidly, is easy to transform, and has well‑characterized genetics, making it the standard host for recombinant DNA cloning.
Correct answer is: Escherichia coli
Q.7 During a polymerase chain reaction (PCR), which step is responsible for the synthesis of new DNA strands?
Denaturation
Annealing
Extension
Cooling
Explanation - In the extension step, DNA polymerase adds nucleotides to the primer’s 3’ end, synthesizing the complementary strand.
Correct answer is: Extension
Q.8 What is a ‘vector’ in the context of recombinant DNA technology?
A device that measures DNA concentration
A DNA molecule that can carry foreign DNA into a host cell
A chemical that stains DNA
A protein that binds DNA
Explanation - Vectors such as plasmids, bacteriophages, or viral genomes are engineered to deliver and replicate foreign DNA inside host cells.
Correct answer is: A DNA molecule that can carry foreign DNA into a host cell
Q.9 Which of the following is NOT a typical step in the creation of a recombinant protein?
Cloning the gene into an expression vector
Transforming the host with the vector
Sequencing the host genome
Purifying the expressed protein
Explanation - Sequencing the host genome is unnecessary for producing a recombinant protein; the focus is on cloning, expression, and purification.
Correct answer is: Sequencing the host genome
Q.10 The enzyme Taq polymerase is preferred in PCR because:
It has high fidelity
It works at low temperatures
It is thermostable and remains active after repeated heating cycles
It cuts DNA at specific sites
Explanation - Taq polymerase, derived from Thermus aquaticus, retains activity at high temperatures, eliminating the need to add fresh enzyme each cycle.
Correct answer is: It is thermostable and remains active after repeated heating cycles
Q.11 In recombinant DNA technology, a ‘promoter’ is used to:
Terminate transcription
Initiate transcription of the downstream gene
Cut DNA at a specific site
Provide antibiotic resistance
Explanation - Promoters are DNA sequences recognized by RNA polymerase to start transcription of a gene placed downstream.
Correct answer is: Initiate transcription of the downstream gene
Q.12 What is the purpose of using a ‘reporter gene’ such as lacZ or GFP in a cloning experiment?
To confer antibiotic resistance
To provide a visual or enzymatic read‑out indicating successful gene insertion and expression
To increase plasmid copy number
To act as a replication origin
Explanation - Reporter genes produce easily detectable signals (color, fluorescence) that confirm the presence and activity of the recombinant construct.
Correct answer is: To provide a visual or enzymatic read‑out indicating successful gene insertion and expression
Q.13 Which method is most commonly used to introduce recombinant plasmids into bacterial cells?
Electroporation
Microinjection
Liposome fusion
Heat shock transformation
Explanation - Heat shock treatment makes bacterial membranes temporarily permeable, allowing plasmid DNA to enter the cells efficiently.
Correct answer is: Heat shock transformation
Q.14 When constructing a recombinant DNA molecule, why is it important to use compatible sticky ends?
They increase the plasmid size
They ensure that the DNA fragments ligate in the correct orientation
They prevent the DNA from being degraded
They enhance transcription efficiency
Explanation - Sticky ends with complementary overhangs base‑pair, allowing fragments to join precisely and maintain the intended reading frame.
Correct answer is: They ensure that the DNA fragments ligate in the correct orientation
Q.15 Which of the following best describes the role of DNA ligase in recombinant DNA technology?
It synthesizes new DNA strands
It cuts DNA at specific sequences
It joins adjacent DNA fragments by forming phosphodiester bonds
It unwinds double‑stranded DNA
Explanation - DNA ligase seals nicks in the sugar‑phosphate backbone, linking the 3’‑OH and 5’‑phosphate groups of adjoining DNA fragments.
Correct answer is: It joins adjacent DNA fragments by forming phosphodiester bonds
Q.16 What is the purpose of a ‘selection marker’ in a cloning vector?
To enhance the expression of the inserted gene
To enable identification of cells that have taken up the vector
To increase plasmid replication speed
To provide a fluorescent signal
Explanation - Selection markers, often antibiotic resistance genes, allow only transformed cells to survive under selective conditions.
Correct answer is: To enable identification of cells that have taken up the vector
Q.17 Which of the following statements about the ‘lac operon’ is true?
It is a eukaryotic transcription factor
It contains genes necessary for lactose metabolism and is regulated by lactose presence
It encodes a viral capsid protein
It is a DNA replication origin
Explanation - The lac operon in E. coli includes lacZ, lacY, and lacA, which are expressed when lactose is present to metabolize it.
Correct answer is: It contains genes necessary for lactose metabolism and is regulated by lactose presence
Q.18 In the context of recombinant DNA, what does ‘codon optimization’ refer to?
Changing DNA sequence to match the preferred codon usage of the host organism
Removing introns from the gene
Adding restriction sites to the gene
Increasing the GC content of the gene
Explanation - Codon optimization improves translation efficiency by adapting the gene to the host’s tRNA abundance and codon bias.
Correct answer is: Changing DNA sequence to match the preferred codon usage of the host organism
Q.19 Which technology allows the direct sequencing of cloned DNA fragments without prior amplification?
Sanger sequencing
Next‑generation sequencing (NGS)
Southern blotting
Northern blotting
Explanation - Sanger (chain‑termination) sequencing can read DNA directly from a plasmid template, whereas NGS typically involves library preparation and amplification.
Correct answer is: Sanger sequencing
Q.20 What is a ‘phagemid’?
A plasmid that contains bacteriophage origin of replication and can be packaged into phage particles
A type of virus used for gene therapy
A DNA polymerase enzyme
A protein that binds DNA
Explanation - Phagemids combine plasmid features with phage packaging signals, useful for phage display and cloning of single‑stranded DNA.
Correct answer is: A plasmid that contains bacteriophage origin of replication and can be packaged into phage particles
Q.21 In recombinant protein production, why is a ‘His‑tag’ often added to the protein’s C‑ or N‑terminus?
To increase the protein’s enzymatic activity
To facilitate purification using metal affinity chromatography
To provide fluorescence
To act as a signal peptide for secretion
Explanation - A stretch of histidine residues binds nickel or cobalt ions, allowing easy purification of the recombinant protein on IMAC columns.
Correct answer is: To facilitate purification using metal affinity chromatography
Q.22 Which of the following is a major ethical concern associated with recombinant DNA technology?
Increased power consumption of labs
Potential creation of harmful organisms or gene flow to the environment
Difficulty in obtaining funding
Longer time required for experiments
Explanation - Recombinant DNA can generate genetically modified organisms that might escape containment, raising biosafety and ecological concerns.
Correct answer is: Potential creation of harmful organisms or gene flow to the environment
Q.23 Which of the following is a commonly used bacterial host for expressing eukaryotic proteins that require post‑translational modifications?
Escherichia coli
Bacillus subtilis
Pichia pastoris
Streptomyces coelicolor
Explanation - P. pastoris, a methylotrophic yeast, can perform many eukaryotic post‑translational modifications such as glycosylation, making it suitable for complex proteins.
Correct answer is: Pichia pastoris
Q.24 In a ligation reaction, the molar ratio of insert to vector is typically set at:
1:10
1:1
3:1
10:1
Explanation - A 3:1 insert:vector ratio maximizes the chance of the insert ligating into the vector while minimizing vector recircularization.
Correct answer is: 3:1
Q.25 What is the function of a ‘terminator’ sequence in a recombinant expression cassette?
To start transcription
To stop transcription and provide stability to the mRNA
To enhance translation efficiency
To provide a site for restriction enzyme cutting
Explanation - Terminator sequences signal RNA polymerase to cease transcription and often contain signals that stabilize the resulting mRNA.
Correct answer is: To stop transcription and provide stability to the mRNA
Q.26 Which of the following best describes ‘site‑directed mutagenesis’?
Random insertion of DNA fragments
Introducing specific nucleotide changes at a defined position in a DNA sequence
Cloning a gene into a vector
Removing all introns from a gene
Explanation - Site‑directed mutagenesis uses designed primers to create precise point mutations, deletions, or insertions in a target gene.
Correct answer is: Introducing specific nucleotide changes at a defined position in a DNA sequence
Q.27 What is the main advantage of using a ‘binary vector’ in Agrobacterium‑mediated plant transformation?
It can replicate in both bacteria and plant cells
It allows separation of the virulence genes from the T‑DNA region, improving safety
It provides a fluorescent marker for selection
It contains multiple origins of replication
Explanation - Binary vectors keep the T‑DNA (gene of interest) separate from the vir genes, reducing the risk of transferring unwanted bacterial genes into the plant genome.
Correct answer is: It allows separation of the virulence genes from the T‑DNA region, improving safety
Q.28 Which of the following enzymes would you use to generate blunt ends from DNA fragments cut with a restriction enzyme that produces sticky ends?
DNA polymerase I
T4 DNA ligase
T4 DNA polymerase
RNAse H
Explanation - T4 DNA polymerase possesses 3’→5’ exonuclease activity that can remove overhangs, creating blunt ends suitable for ligation.
Correct answer is: T4 DNA polymerase
Q.29 In the context of recombinant DNA, what does the term ‘copy number’ refer to?
The number of genes in a genome
The number of plasmid copies present in each host cell
The number of restriction sites in a vector
The number of amino acids in a protein
Explanation - Copy number indicates how many copies of a plasmid are maintained per cell, influencing yield of recombinant DNA or protein.
Correct answer is: The number of plasmid copies present in each host cell
Q.30 What is the purpose of adding a ‘signal peptide’ to a recombinant protein expressed in a bacterial system?
To increase the protein’s molecular weight
To direct the protein to the periplasmic space or extracellular medium
To confer antibiotic resistance
To enhance transcription
Explanation - Signal peptides are short N‑terminal sequences that guide the nascent protein through the secretory pathway, allowing easier purification.
Correct answer is: To direct the protein to the periplasmic space or extracellular medium
Q.31 Which of the following is a characteristic of a ‘shuttle vector’?
It can replicate in both prokaryotic and eukaryotic cells
It contains only a bacterial origin of replication
It is unable to carry large DNA fragments
It does not require a selectable marker
Explanation - Shuttle vectors possess origins of replication and selectable markers for two different host types, enabling DNA transfer between them.
Correct answer is: It can replicate in both prokaryotic and eukaryotic cells
Q.32 Which of the following is a common method for confirming the presence of an insert in a recombinant plasmid?
Western blotting
Restriction digest analysis followed by gel electrophoresis
Protein crystallography
Flow cytometry
Explanation - Digesting the plasmid with specific enzymes and visualizing fragment sizes on an agarose gel can verify successful insertion.
Correct answer is: Restriction digest analysis followed by gel electrophoresis
Q.33 What does the term ‘heterologous expression’ mean?
Expression of a gene in its native organism
Expression of a gene in a different host species than the one it originates from
Expression of multiple genes simultaneously
Expression of genes without a promoter
Explanation - Heterologous expression involves producing a protein in a host that does not naturally carry the gene, often to simplify production.
Correct answer is: Expression of a gene in a different host species than the one it originates from
Q.34 Which of the following is a major advantage of using a ‘baculovirus expression system’ for recombinant protein production?
Low cost of media
Ability to express large, complex eukaryotic proteins with proper folding and post‑translational modifications
Rapid growth of host cells
Resistance to all antibiotics
Explanation - Baculovirus infects insect cells, which can perform many eukaryotic PTMs, making them suitable for producing functional complex proteins.
Correct answer is: Ability to express large, complex eukaryotic proteins with proper folding and post‑translational modifications
Q.35 In the context of recombinant DNA, what does the term ‘gene gun’ refer to?
A device that uses high‑velocity particles to deliver DNA into cells
A software for designing primers
A method for sequencing DNA
A type of electrophoresis apparatus
Explanation - The gene gun (biolistic particle delivery) propels DNA-coated micro‑projectiles into plant or animal cells for transformation.
Correct answer is: A device that uses high‑velocity particles to deliver DNA into cells
Q.36 Which of the following best describes a ‘synthetic promoter’?
A promoter derived from a viral genome
A promoter engineered by combining elements from different sources to achieve desired expression levels
A promoter that cannot be recognized by any polymerase
A promoter that only functions in prokaryotes
Explanation - Synthetic promoters are designed to fine‑tune transcription by mixing core, enhancer, and regulatory sequences.
Correct answer is: A promoter engineered by combining elements from different sources to achieve desired expression levels
Q.37 During a Southern blot, which of the following is used to detect a specific DNA fragment?
A radioactive or fluorescent labeled DNA probe
An antibody against DNA
A DNA polymerase
A restriction enzyme
Explanation - Probes hybridize to complementary DNA on the blot, allowing visualization of the target fragment.
Correct answer is: A radioactive or fluorescent labeled DNA probe
Q.38 What is the main function of the ‘lacI’ gene in a plasmid vector that contains the lac operon?
Encodes the enzyme beta‑galactosidase
Provides resistance to tetracycline
Produces the Lac repressor protein that blocks transcription in the absence of IPTG
Acts as a promoter for the multiple cloning site
Explanation - LacI protein binds to the operator, preventing transcription; IPTG acts as an inducer to release this repression.
Correct answer is: Produces the Lac repressor protein that blocks transcription in the absence of IPTG
Q.39 Which of the following statements about ‘CRISPR‑Cas9’ in the context of recombinant DNA technology is correct?
It is a type of restriction enzyme that cuts at random sites
It provides a programmable system for precise genome editing by guiding Cas9 to a specific DNA sequence
It is used to amplify DNA fragments in PCR
It is a plasmid replication origin
Explanation - CRISPR‑Cas9 uses a guide RNA to direct the Cas9 nuclease to a target DNA, enabling targeted cuts and subsequent modifications.
Correct answer is: It provides a programmable system for precise genome editing by guiding Cas9 to a specific DNA sequence
Q.40 Why is it important to include a ‘ribosome binding site’ (RBS) upstream of a coding sequence in a bacterial expression construct?
To start DNA replication
To ensure proper transcription termination
To facilitate the recruitment of ribosomes for translation initiation
To provide antibiotic resistance
Explanation - The RBS (Shine‑Dalgarno sequence) aligns the ribosome with the start codon, allowing efficient translation of the mRNA.
Correct answer is: To facilitate the recruitment of ribosomes for translation initiation
Q.41 In recombinant DNA, what does the term ‘vector backbone’ refer to?
The DNA segment that contains the gene of interest
All essential elements of the vector excluding the multiple cloning site and insert
The promoter region
The antibiotic resistance gene
Explanation - The backbone includes the origin of replication, selectable marker, and other functional regions needed for maintenance and selection.
Correct answer is: All essential elements of the vector excluding the multiple cloning site and insert
Q.42 Which technique is commonly used to amplify a specific DNA fragment before cloning it into a vector?
Gel electrophoresis
Polymerase chain reaction (PCR)
Southern blotting
DNA fingerprinting
Explanation - PCR exponentially amplifies a targeted DNA region using primers, making enough material for downstream cloning steps.
Correct answer is: Polymerase chain reaction (PCR)
Q.43 What is a ‘fusion protein’ in recombinant DNA technology?
A protein formed by the covalent joining of two or more distinct protein domains, often to aid purification or detection
A protein that cannot be expressed in bacteria
A protein that has been chemically cross‑linked
A protein that is encoded by multiple genes
Explanation - Fusion proteins combine functional domains (e.g., tags, enzymes) to simplify downstream processing or assay development.
Correct answer is: A protein formed by the covalent joining of two or more distinct protein domains, often to aid purification or detection
Q.44 Which of the following best describes the purpose of a ‘negative selection marker’ such as sacB in cloning?
It kills cells that have taken up the vector
It allows growth only of cells that have the plasmid
It counter‑selects cells that retain the vector after a recombination event
It enhances plasmid copy number
Explanation - SacB encodes levansucrase, which is lethal in many bacteria when grown on sucrose, enabling selection against cells that have not undergone the desired recombination.
Correct answer is: It counter‑selects cells that retain the vector after a recombination event
Q.45 During the production of a recombinant vaccine, why might a scientist choose to express the antigen in a mammalian cell line rather than in E. coli?
Mammalian cells grow faster
Mammalian cells are cheaper to culture
Mammalian cells can perform proper protein folding and post‑translational modifications that are essential for antigenicity
E. coli cannot replicate plasmids
Explanation - Many vaccine antigens require correct glycosylation and disulfide bond formation, which bacterial systems cannot reliably provide.
Correct answer is: Mammalian cells can perform proper protein folding and post‑translational modifications that are essential for antigenicity
Q.46 Which of the following statements about ‘RNA interference (RNAi)’ is true in the context of recombinant technology?
RNAi is used to amplify DNA fragments
RNAi involves introducing short hairpin RNAs (shRNA) to silence specific genes in host cells
RNAi increases transcription of the target gene
RNAi replaces the need for a promoter
Explanation - shRNA expressed from recombinant vectors can be processed into siRNA, leading to sequence‑specific mRNA degradation and gene knock‑down.
Correct answer is: RNAi involves introducing short hairpin RNAs (shRNA) to silence specific genes in host cells
Q.47 What is the main purpose of ‘codon bias’ analysis when designing a gene for expression in a heterologous host?
To identify restriction sites
To select a promoter
To adapt the gene’s codon usage to the host’s tRNA abundance for higher expression
To determine the gene’s GC content
Explanation - Matching codon usage to the host’s preferred codons reduces translational pauses and boosts protein yield.
Correct answer is: To adapt the gene’s codon usage to the host’s tRNA abundance for higher expression
Q.48 In the context of recombinant DNA, what does ‘genomic library’ refer to?
A collection of plasmids each containing a different fragment of the organism’s entire genome
A database of protein structures
A set of primers for PCR
A series of restriction enzymes
Explanation - Genomic libraries are constructed by fragmenting genomic DNA and cloning the pieces into vectors, allowing screening for genes of interest.
Correct answer is: A collection of plasmids each containing a different fragment of the organism’s entire genome
Q.49 Which method is most suitable for delivering recombinant DNA into mammalian cells in vitro?
Heat shock transformation
Electroporation
Phage infection
Conjugation
Explanation - Electroporation creates temporary pores in mammalian cell membranes using an electric pulse, allowing DNA uptake.
Correct answer is: Electroporation
Q.50 What does the term ‘inducible promoter’ mean?
A promoter that is always active
A promoter that can be turned on or off by adding a specific chemical inducer
A promoter that cannot be regulated
A promoter that only works in eukaryotic cells
Explanation - Inducible promoters (e.g., lac, araBAD) allow controlled expression of the downstream gene in response to an inducer like IPTG or arabinose.
Correct answer is: A promoter that can be turned on or off by adding a specific chemical inducer
Q.51 Which of the following is a key advantage of using a ‘synthetic gene’ (de‑novo synthesized) over a naturally isolated gene for recombinant expression?
Lower cost
Freedom to incorporate codon optimization, removal of problematic sequences, and addition of tags
Higher mutation rate
Easier to clone into any vector
Explanation - Synthetic genes can be designed to improve expression, eliminate restriction sites, and include desired features before synthesis.
Correct answer is: Freedom to incorporate codon optimization, removal of problematic sequences, and addition of tags
Q.52 In recombinant DNA technology, what is the purpose of a ‘poly‑A tail’ in a eukaryotic expression construct?
To signal transcription termination and enhance mRNA stability and translation efficiency
To act as a promoter
To serve as a restriction site
To provide antibiotic resistance
Explanation - The poly‑A tail protects mRNA from degradation and aids in nuclear export and translation initiation.
Correct answer is: To signal transcription termination and enhance mRNA stability and translation efficiency
Q.53 Which of the following best describes a ‘cDNA library’?
A collection of DNA fragments representing the entire genome of an organism
A collection of DNA sequences reverse‑transcribed from mRNA, representing expressed genes
A set of synthetic DNA fragments designed for vaccine development
A library of plasmids containing promoter sequences
Explanation - cDNA libraries are generated by reverse transcribing mRNA, providing a snapshot of genes actively expressed in a tissue.
Correct answer is: A collection of DNA sequences reverse‑transcribed from mRNA, representing expressed genes
Q.54 Which of the following is NOT a typical component of a mammalian expression vector?
SV40 origin of replication
CMV promoter
Kanamycin resistance gene
Polyadenylation signal
Explanation - Kanamycin resistance is used for bacterial selection; mammalian vectors usually employ different selectable markers such as neomycin (G418) resistance.
Correct answer is: Kanamycin resistance gene
Q.55 What is the primary reason to use ‘high‑copy number plasmids’ when producing recombinant protein?
To increase the stability of the host genome
To ensure low metabolic burden on the host
To generate a larger amount of plasmid DNA and therefore higher levels of gene expression
To reduce the need for antibiotics
Explanation - High‑copy vectors amplify the number of gene copies per cell, leading to greater transcription and protein production.
Correct answer is: To generate a larger amount of plasmid DNA and therefore higher levels of gene expression
Q.56 Which technique would you use to introduce a precise point mutation into a plasmid without leaving any extra sequences behind?
Random mutagenesis
Site‑directed mutagenesis using overlapping PCR
Restriction enzyme digestion and ligation
CRISPR‑Cas9 with non‑homologous end joining
Explanation - Overlap‑extension PCR can insert specific base changes while preserving the plasmid backbone without additional scars.
Correct answer is: Site‑directed mutagenesis using overlapping PCR
Q.57 In a recombinant DNA construct for secreted protein production in yeast, which sequence is essential for directing the protein to the secretory pathway?
Kozak sequence
Signal peptide
TATA box
Origin of replication
Explanation - Signal peptides are N‑terminal leader sequences that target nascent polypeptides to the endoplasmic reticulum for secretion.
Correct answer is: Signal peptide
Q.58 Which of the following best explains why a ‘temperature‑sensitive’ plasmid might be used in cloning?
It replicates only at low temperatures, allowing easy curing of the plasmid by shifting to a higher temperature
It confers resistance to temperature‑related stress
It increases the speed of bacterial growth
It changes the host’s metabolism at different temperatures
Explanation - Temperature‑sensitive replication origins permit plasmid loss when cultures are grown at a non‑permissive temperature, useful for subsequent steps.
Correct answer is: It replicates only at low temperatures, allowing easy curing of the plasmid by shifting to a higher temperature
Q.59 What is the purpose of using ‘Blue/White screening’ in cloning?
To differentiate between plasmids that contain an insert and those that do not based on colony color
To select for antibiotic resistance
To measure plasmid copy number
To identify high‑expressing colonies
Explanation - Insertion of a DNA fragment disrupts the lacZ α‑fragment, resulting in white colonies, whereas non‑recombinant colonies remain blue on X‑gal/IPTG plates.
Correct answer is: To differentiate between plasmids that contain an insert and those that do not based on colony color
Q.60 Which of the following is a potential advantage of using ‘viral vectors’ over plasmid vectors for gene delivery in mammalian cells?
Lower cost of production
Higher transduction efficiency and ability to infect non‑dividing cells
Easier purification
No risk of immune response
Explanation - Viral vectors can efficiently deliver genetic material into a wide range of cell types, including quiescent cells, making them powerful for therapeutic applications.
Correct answer is: Higher transduction efficiency and ability to infect non‑dividing cells
Q.61 Which of the following enzymes is used to join DNA fragments that have been cut with a restriction enzyme producing sticky ends?
DNA polymerase
RNA ligase
T4 DNA ligase
Helicase
Explanation - T4 DNA ligase catalyzes the formation of phosphodiester bonds between adjacent nucleotides, sealing sticky ends together.
Correct answer is: T4 DNA ligase
Q.62 What is the function of the ‘poly‑histidine tag’ (His‑tag) when expressed at the C‑terminus of a recombinant protein?
To increase protein solubility
To target the protein to the nucleus
To enable purification by nickel affinity chromatography
To act as a transcriptional activator
Explanation - His‑tags bind to nickel or cobalt ions immobilized on a resin, allowing selective capture and elution of the tagged protein.
Correct answer is: To enable purification by nickel affinity chromatography
Q.63 In the context of recombinant DNA, which of the following best describes the term ‘knock‑in’?
A technique to delete a gene from the genome
A method to insert a specific gene at a defined locus in the genome
A strategy to over‑express a gene from a plasmid
A way to silence gene expression using RNAi
Explanation - Knock‑in approaches introduce a gene into a precise genomic location, often via homologous recombination or CRISPR‑mediated HDR.
Correct answer is: A method to insert a specific gene at a defined locus in the genome
Q.64 Why might a researcher choose to use a ‘low‑copy number’ plasmid for cloning toxic genes?
Low‑copy plasmids are easier to purify
They reduce the metabolic burden and toxicity caused by high expression of the toxic product
They increase antibiotic resistance
They allow for faster bacterial growth
Explanation - Limiting the number of plasmid copies curtails expression levels, preventing lethal effects on the host cell.
Correct answer is: They reduce the metabolic burden and toxicity caused by high expression of the toxic product
Q.65 Which of the following is a commonly used method to verify the sequence of a recombinant plasmid after cloning?
Northern blotting
Sanger DNA sequencing
ELISA
Mass spectrometry
Explanation - Sanger sequencing reads the nucleotide order of the cloned insert, confirming its integrity and orientation.
Correct answer is: Sanger DNA sequencing
Q.66 In the production of recombinant insulin, which host organism is most frequently employed?
Saccharomyces cerevisiae
Escherichia coli
Bacillus subtilis
HeLa cells
Explanation - E. coli was the first organism used to produce human insulin commercially, thanks to its rapid growth and well‑established expression systems.
Correct answer is: Escherichia coli
Q.67 Which of the following is a major limitation of using bacterial expression systems for producing eukaryotic proteins?
Inability to grow to high cell densities
Lack of proper protein folding and post‑translational modifications like glycosylation
Requirement for expensive media
Slow growth rate
Explanation - Bacteria lack the cellular machinery for many eukaryotic PTMs, which can affect protein activity and stability.
Correct answer is: Lack of proper protein folding and post‑translational modifications like glycosylation
Q.68 What does the term ‘transformation efficiency’ refer to in recombinant DNA work?
The speed at which DNA is amplified by PCR
The percentage of cells that successfully take up foreign DNA during a transformation procedure
The ability of a plasmid to replicate in a host
The rate of protein production from a recombinant gene
Explanation - Transformation efficiency is measured as colony‑forming units per microgram of DNA and reflects how well the protocol introduces DNA into cells.
Correct answer is: The percentage of cells that successfully take up foreign DNA during a transformation procedure
Q.69 Which of the following is a commonly used selectable marker for mammalian cell culture?
Ampicillin resistance
Kanamycin resistance
Neomycin resistance (G418)
Chloramphenicol resistance
Explanation - G418 selects for mammalian cells that have integrated a neomycin resistance gene, allowing stable expression of recombinant constructs.
Correct answer is: Neomycin resistance (G418)
Q.70 What is the purpose of a ‘spacer’ sequence between a promoter and the ribosome binding site in a bacterial expression vector?
To increase plasmid copy number
To prevent transcriptional read‑through
To ensure optimal distance for efficient translation initiation
To encode a terminator
Explanation - A spacer positions the RBS at an appropriate distance from the start codon, enhancing translation efficiency.
Correct answer is: To ensure optimal distance for efficient translation initiation
Q.71 Which of the following best describes a ‘bio‑reactor’ in the context of recombinant protein production?
A device used for DNA sequencing
A large‑scale vessel where cultured cells or microbes are grown under controlled conditions to produce recombinant proteins
A type of electrophoresis gel
A software tool for designing primers
Explanation - Bioreactors allow precise control over temperature, pH, oxygen, and nutrient supply, optimizing protein yield at industrial scales.
Correct answer is: A large‑scale vessel where cultured cells or microbes are grown under controlled conditions to produce recombinant proteins
Q.72 In a recombinant DNA experiment, why might a scientist include a ‘stop codon’ immediately downstream of a His‑tag sequence?
To prevent transcription of downstream genes
To ensure that translation terminates after the tagged protein, avoiding fusion with unwanted residues
To increase plasmid stability
To enhance promoter activity
Explanation - A stop codon signals the ribosome to end translation, ensuring the protein ends where intended.
Correct answer is: To ensure that translation terminates after the tagged protein, avoiding fusion with unwanted residues
Q.73 Which of the following is a reason to use a ‘fusion partner’ such as maltose‑binding protein (MBP) when expressing a recombinant protein in E. coli?
To confer antibiotic resistance
To improve solubility and folding of the target protein
To increase the size of the plasmid
To act as a transcription factor
Explanation - Fusion partners like MBP enhance the solubility of otherwise insoluble proteins, facilitating proper folding and downstream purification.
Correct answer is: To improve solubility and folding of the target protein
Q.74 What does the term ‘heteroduplex’ refer to in the context of recombinant DNA techniques?
A DNA molecule containing regions of mismatched base pairs formed by annealing of two different strands
A DNA fragment that has been digested by restriction enzymes
A plasmid that cannot replicate
A double‑stranded RNA molecule
Explanation - Heteroduplexes arise when strands from different sources hybridize, useful for detecting mutations or recombination events.
Correct answer is: A DNA molecule containing regions of mismatched base pairs formed by annealing of two different strands
Q.75 Which of the following statements about ‘phage display’ is true?
It involves inserting a gene into a bacterial chromosome
It displays peptide or protein fragments on the surface of bacteriophages for selection of binding partners
It is a method to increase plasmid copy number
It uses electroporation to introduce DNA into mammalian cells
Explanation - Phage display links genotype (DNA) with phenotype (displayed peptide), enabling rapid screening of libraries for high‑affinity binders.
Correct answer is: It displays peptide or protein fragments on the surface of bacteriophages for selection of binding partners
Q.76 In the design of a recombinant vector for plant transformation, what is the role of the ‘nos terminator’?
To provide a site for restriction enzyme cutting
To terminate transcription of the transgene in plant cells
To increase plasmid replication in bacteria
To confer herbicide resistance
Explanation - The nopaline synthase (nos) terminator signals transcription termination and polyadenylation in plant expression systems.
Correct answer is: To terminate transcription of the transgene in plant cells
Q.77 Which of the following is an advantage of using a ‘self‑cleaving 2A peptide’ in a multicistronic expression construct?
It enables simultaneous expression of multiple proteins from a single open reading frame
It increases plasmid stability
It provides antibiotic resistance
It reduces transcriptional noise
Explanation - 2A peptides cause ribosomal skipping, resulting in separate proteins being produced from one mRNA without needing multiple promoters.
Correct answer is: It enables simultaneous expression of multiple proteins from a single open reading frame
Q.78 Which of the following best describes a ‘genomic integration’ event in recombinant DNA technology?
Insertion of a plasmid that replicates independently of the host genome
Stable incorporation of a DNA construct into the host chromosome, often via homologous recombination
Transient expression from an episomal vector
Deletion of a chromosomal region
Explanation - Genomic integration ensures long‑term expression and inheritance of the transgene during cell division.
Correct answer is: Stable incorporation of a DNA construct into the host chromosome, often via homologous recombination
Q.79 In a recombinant DNA construct, why might a researcher include a ‘Kozak sequence’ upstream of the start codon?
To enhance transcription initiation in prokaryotes
To promote efficient translation initiation in eukaryotic cells
To provide a restriction site
To increase plasmid copy number
Explanation - The Kozak consensus sequence (GCCACCATGG) surrounds the start codon and enhances ribosome binding in eukaryotes, increasing protein expression.
Correct answer is: To promote efficient translation initiation in eukaryotic cells
Q.80 Which of the following is a typical method for confirming the correct orientation of an insert in a plasmid?
DNA sequencing only
Digesting with two restriction enzymes that flank the insert and analyzing fragment sizes on a gel
Measuring plasmid size by spectrophotometry
Observing colony color on X‑gal plates
Explanation - A double digest yields fragments of predictable sizes depending on orientation, allowing verification by gel electrophoresis.
Correct answer is: Digesting with two restriction enzymes that flank the insert and analyzing fragment sizes on a gel
Q.81 What is the primary advantage of using a ‘dual‑promoter vector’ for recombinant protein production?
It allows simultaneous expression of two different genes from separate promoters within the same construct
It increases plasmid copy number
It provides resistance to two different antibiotics
It eliminates the need for a selectable marker
Explanation - Dual‑promoter vectors enable co‑expression of a protein of interest and a helper protein (e.g., chaperone) to improve folding or activity.
Correct answer is: It allows simultaneous expression of two different genes from separate promoters within the same construct
Q.82 Which of the following is a common method to increase the solubility of a recombinant protein expressed in E. coli?
Expressing the protein at high temperature
Adding a strong ribosome binding site
Co‑expressing molecular chaperones or using fusion tags like GST
Increasing the antibiotic concentration
Explanation - Chaperones assist folding, and tags like glutathione‑S‑transferase (GST) increase solubility, reducing inclusion body formation.
Correct answer is: Co‑expressing molecular chaperones or using fusion tags like GST
Q.83 What is the purpose of using a ‘poly‑A polymerase’ in the preparation of a eukaryotic expression construct?
To add a poly‑A tail to the 3’ end of the mRNA transcript for stability and translation efficiency
To cut DNA at restriction sites
To ligate DNA fragments together
To initiate transcription
Explanation - Poly‑A polymerase adds adenine residues to the mRNA 3’ end, a feature important for nuclear export and translation in eukaryotes.
Correct answer is: To add a poly‑A tail to the 3’ end of the mRNA transcript for stability and translation efficiency
Q.84 Which of the following best describes a ‘synthetic biology chassis’ in the context of recombinant DNA?
A standardized host organism engineered to accept and reliably express synthetic genetic circuits
A type of restriction enzyme
A plasmid that cannot replicate
A software platform for DNA design
Explanation - Chassis organisms (e.g., E. coli, S. cerevisiae) are optimized for predictability and modularity, serving as platforms for synthetic DNA constructs.
Correct answer is: A standardized host organism engineered to accept and reliably express synthetic genetic circuits
Q.85 Why is the use of a ‘terminator’ sequence important in a recombinant construct intended for high‑level expression in plants?
It enhances transcription initiation
It provides a signal for protein secretion
It ensures proper transcription termination and polyadenylation, stabilizing the mRNA
It increases plasmid copy number
Explanation - Terminator sequences like the nos or 35S terminator stop transcription and add poly‑A signals, improving mRNA stability and expression.
Correct answer is: It ensures proper transcription termination and polyadenylation, stabilizing the mRNA
Q.86 Which of the following technologies enables the rapid assembly of multiple DNA fragments in a single, scar‑less reaction?
Gibson Assembly
Southern blotting
Blue/White screening
PCR‑RFLP
Explanation - Gibson Assembly uses overlapping ends and a mixture of exonuclease, polymerase, and ligase to join fragments seamlessly in one step.
Correct answer is: Gibson Assembly
Q.87 In the context of recombinant DNA, what does the term ‘episomal vector’ mean?
A vector that integrates into the host chromosome
A vector that replicates extrachromosomally as a separate DNA molecule
A vector that cannot be replicated
A vector that expresses only RNA
Explanation - Episomal vectors (e.g., certain viral vectors, yeast 2µ plasmids) remain independent of the host genome, allowing transient expression.
Correct answer is: A vector that replicates extrachromosomally as a separate DNA molecule
Q.88 Which of the following is the most common method for delivering recombinant DNA into plant cells for stable transformation?
Electroporation
Agrobacterium‑mediated transformation
Microinjection
Liposome transfection
Explanation - Agrobacterium transfers T‑DNA into plant genomes efficiently, making it the preferred method for generating transgenic plants.
Correct answer is: Agrobacterium‑mediated transformation
Q.89 What is the function of the ‘tet‑operator’ (tetO) in a tetracycline‑inducible expression system?
It acts as a promoter for the gene of interest
It binds the TetR repressor, blocking transcription in the absence of tetracycline
It provides antibiotic resistance
It serves as a ribosome binding site
Explanation - In the Tet system, TetR binds tetO to repress transcription; addition of tetracycline releases TetR, allowing expression.
Correct answer is: It binds the TetR repressor, blocking transcription in the absence of tetracycline
Q.90 Which of the following statements about the ‘CRISPR‑Cas12a (Cpf1)’ system is correct?
Cas12a creates blunt ends rather than staggered cuts
Cas12a requires a PAM sequence of TTTV (where V = A, C, or G)
Cas12a cannot be used for gene editing
Cas12a does not require a guide RNA
Explanation - Cas12a (Cpf1) recognizes a T‑rich PAM (TTTV) and generates staggered cuts, offering an alternative to Cas9 for certain applications.
Correct answer is: Cas12a requires a PAM sequence of TTTV (where V = A, C, or G)
Q.91 In recombinant DNA, what is the purpose of a ‘silent mutation’ introduced during site‑directed mutagenesis?
To change the amino acid sequence
To alter the protein’s activity
To modify codon usage without altering the encoded amino acid
To create a new restriction site
Explanation - Silent mutations change the DNA codon but not the protein sequence, useful for optimizing expression or removing unwanted restriction sites.
Correct answer is: To modify codon usage without altering the encoded amino acid
Q.92 Which of the following best describes the principle of ‘RNA‑based vaccine’ design using recombinant DNA technology?
DNA is directly injected into patients
A plasmid is used to express viral proteins in host cells
Synthetic mRNA encoding the antigen is produced from a DNA template and delivered to cells to trigger an immune response
Viral vectors are used to integrate the antigen gene into the host genome
Explanation - Recombinant DNA is used to generate an in‑vitro‑transcribed mRNA vaccine, which, once delivered, is translated into antigenic protein inside host cells.
Correct answer is: Synthetic mRNA encoding the antigen is produced from a DNA template and delivered to cells to trigger an immune response
Q.93 What is the main advantage of using a ‘self‑replicating RNA (replicon)’ vector for vaccine development?
It integrates into the host genome
It provides high levels of antigen expression without the need for DNA delivery
It confers antibiotic resistance
It reduces the size of the antigen gene
Explanation - Replicons amplify themselves in the cytoplasm, leading to strong antigen production while avoiding nuclear entry and integration risks.
Correct answer is: It provides high levels of antigen expression without the need for DNA delivery
Q.94 Which of the following is a typical characteristic of a ‘conditional expression system’ in recombinant DNA work?
Expression is constitutive and cannot be turned off
Expression can be turned on or off by external stimuli such as temperature, chemicals, or light
The vector cannot be replicated
The gene of interest is deleted after expression
Explanation - Conditional systems (e.g., temperature‑sensitive promoters, tetracycline‑inducible) enable precise control over when and how much protein is produced.
Correct answer is: Expression can be turned on or off by external stimuli such as temperature, chemicals, or light
Q.95 In the context of recombinant DNA, what does the term ‘homology‑directed repair’ (HDR) refer to?
Repair of DNA double‑strand breaks using a homologous DNA template to introduce precise edits
Random insertion of DNA fragments
Repair of RNA molecules
A method for increasing plasmid copy number
Explanation - HDR uses a supplied DNA template with desired changes to guide accurate repair after Cas9 or other nuclease‑induced cuts.
Correct answer is: Repair of DNA double‑strand breaks using a homologous DNA template to introduce precise edits
Q.96 Which of the following is a common strategy to reduce proteolytic degradation of recombinant proteins in bacterial expression systems?
Expressing the protein at 37 °C
Using protease‑deficient host strains
Adding more antibiotics
Increasing plasmid copy number
Explanation - Protease‑deficient strains (e.g., BL21(DE3) lacking Lon and OmpT) reduce degradation of sensitive recombinant proteins.
Correct answer is: Using protease‑deficient host strains
Q.97 Which of the following best explains why a ‘bicistronic vector’ may be used in recombinant expression?
To express two unrelated genes from a single promoter using an internal ribosome entry site (IRES)
To increase plasmid stability
To provide dual antibiotic resistance
To create a larger plasmid backbone
Explanation - Bicistronic constructs use an IRES to allow ribosomes to initiate translation of a second open reading frame downstream of the first, enabling co‑expression.
Correct answer is: To express two unrelated genes from a single promoter using an internal ribosome entry site (IRES)
Q.98 In recombinant DNA, what is the purpose of a ‘splicing donor/acceptor site’ in a construct designed for expression in eukaryotic cells?
To allow removal of introns from the primary transcript, generating a mature mRNA
To increase plasmid replication speed
To provide a restriction site for cloning
To confer antibiotic resistance
Explanation - Splice donor and acceptor sequences guide the splicing machinery to excise introns, producing a functional mRNA for translation.
Correct answer is: To allow removal of introns from the primary transcript, generating a mature mRNA
Q.99 Which of the following methods can be employed to produce a recombinant protein that requires disulfide bond formation?
Expression in the cytoplasm of standard E. coli strains
Expression in the periplasmic space of E. coli or in eukaryotic hosts
Expression at 42 °C
Using a high‑copy number plasmid
Explanation - The periplasm and eukaryotic secretory pathways provide oxidative environments conducive to disulfide bond formation.
Correct answer is: Expression in the periplasmic space of E. coli or in eukaryotic hosts
Q.100 What does the term ‘metabolic burden’ refer to in the context of recombinant DNA production in microbial hosts?
The increase in plasmid copy number
The strain placed on the host’s cellular resources due to overexpression of recombinant proteins
The resistance to antibiotics
The speed of DNA replication
Explanation - High-level expression diverts energy and precursors away from growth, potentially slowing cell division and reducing yields.
Correct answer is: The strain placed on the host’s cellular resources due to overexpression of recombinant proteins
Q.101 Which of the following is an example of a ‘post‑translational modification’ that can affect recombinant protein activity?
DNA replication
Glycosylation
Transcription
RNA splicing
Explanation - Glycosylation adds carbohydrate groups to proteins, influencing stability, activity, and immunogenicity, especially in therapeutic proteins.
Correct answer is: Glycosylation
Q.102 Why is the use of a ‘chromatin insulator’ sometimes incorporated into mammalian expression vectors?
To increase plasmid replication speed
To prevent positional effects and silencing of the transgene due to surrounding chromatin
To confer antibiotic resistance
To act as a promoter
Explanation - Insulators buffer the transgene from nearby repressive chromatin, leading to more consistent expression across integration sites.
Correct answer is: To prevent positional effects and silencing of the transgene due to surrounding chromatin
Q.103 In the design of a recombinant construct for secreted antibody fragments, which region must be included to ensure proper secretion?
A poly‑A tail
A signal peptide sequence
A terminator sequence
An origin of replication
Explanation - Signal peptides direct the nascent peptide into the secretory pathway, resulting in secretion of the antibody fragment into the culture medium.
Correct answer is: A signal peptide sequence
Q.104 Which of the following is a characteristic of the ‘pUC’ series of plasmid vectors?
Low copy number and no multiple cloning site
High copy number and a lacZ α‑fragment for blue/white screening
Contains a eukaryotic origin of replication
Provides resistance to tetracycline only
Explanation - pUC vectors replicate to high copy numbers and include an MCS within lacZ α‑fragment, enabling blue/white screening for recombinants.
Correct answer is: High copy number and a lacZ α‑fragment for blue/white screening
Q.105 What is the main purpose of adding an ‘internal ribosome entry site’ (IRES) in a multicistronic vector?
To initiate transcription
To allow cap‑independent translation initiation of downstream open reading frames
To provide antibiotic resistance
To increase plasmid size
Explanation - IRES elements recruit ribosomes directly to internal sites, enabling translation of multiple proteins from a single mRNA.
Correct answer is: To allow cap‑independent translation initiation of downstream open reading frames
Q.106 Which of the following best explains why a ‘synthetic minimal promoter’ might be used in a recombinant construct?
To reduce background transcription and achieve tight regulation of gene expression
To increase plasmid copy number
To provide a selectable marker
To enhance DNA replication speed
Explanation - Minimal promoters contain only essential elements, minimizing leaky expression and allowing precise control via added regulatory sequences.
Correct answer is: To reduce background transcription and achieve tight regulation of gene expression