Q.1 What does the abbreviation “DNA” stand for?
Deoxyribonucleic Acid
Dideoxy Nucleic Acid
Double Nucleotide Arrangement
Diatomic Nucleic Acid
Explanation - DNA is short for Deoxyribonucleic Acid, the molecule that carries genetic information in cells.
Correct answer is: Deoxyribonucleic Acid
Q.2 Which enzyme cuts DNA at specific sequences to create fragments for recombinant DNA technology?
DNA polymerase
Ligase
Restriction endonuclease
RNAse H
Explanation - Restriction endonucleases recognize specific DNA sequences and cleave the phosphodiester bond, generating defined fragments.
Correct answer is: Restriction endonuclease
Q.3 In a cloning vector, the multiple cloning site (MCS) is:
A region that codes for antibiotic resistance
A series of unique restriction sites
The origin of replication
A promoter for gene expression
Explanation - The MCS contains several restriction sites that allow insertion of a DNA fragment using various enzymes.
Correct answer is: A series of unique restriction sites
Q.4 Which of the following is a commonly used bacterial host for recombinant DNA experiments?
Bacillus subtilis
Saccharomyces cerevisiae
Escherichia coli
Pseudomonas aeruginosa
Explanation - E. coli is easy to grow, transform, and manipulate, making it a standard host for cloning.
Correct answer is: Escherichia coli
Q.5 The enzyme DNA ligase is used in recombinant DNA technology to:
Separate DNA strands
Join DNA fragments together
Synthesize RNA from DNA
Repair mismatched bases
Explanation - DNA ligase catalyzes the formation of phosphodiester bonds between adjacent nucleotides, sealing nicks in the backbone.
Correct answer is: Join DNA fragments together
Q.6 What is the purpose of a selectable marker in a plasmid vector?
To increase plasmid size
To allow growth of only transformed cells
To enhance DNA replication speed
To inhibit host cell metabolism
Explanation - Selectable markers (e.g., antibiotic resistance genes) enable identification of cells that have taken up the plasmid.
Correct answer is: To allow growth of only transformed cells
Q.7 Which of the following is a viral vector commonly used for gene therapy?
Adeno-associated virus (AAV)
Bacteriophage λ
F plasmid
Yeast artificial chromosome (YAC)
Explanation - AAV is a non‑pathogenic virus that can deliver therapeutic genes to human cells efficiently.
Correct answer is: Adeno-associated virus (AAV)
Q.8 The term “recombinant DNA” refers to:
DNA that is replicated in a test tube
DNA that has been artificially joined from two different sources
DNA that is naturally occurring in a hybrid organism
DNA that has been damaged by radiation
Explanation - Recombinant DNA is formed when DNA fragments from different origins are combined into a single molecule.
Correct answer is: DNA that has been artificially joined from two different sources
Q.9 Which of the following best describes a “promoter” in a recombinant plasmid?
A sequence that initiates transcription of a downstream gene
A region that terminates transcription
A DNA segment that encodes ribosomal RNA
A binding site for DNA polymerase during replication
Explanation - Promoters are DNA sequences where RNA polymerase binds to start transcription of the gene placed downstream.
Correct answer is: A sequence that initiates transcription of a downstream gene
Q.10 In the context of recombinant DNA technology, what is a “host cell”?
A cell that provides nutrients for bacterial growth
A cell that contains the recombinant DNA after transformation
A cell that produces restriction enzymes
A cell that degrades foreign DNA
Explanation - The host cell is the organism (often bacteria) that takes up and maintains the recombinant plasmid for further use.
Correct answer is: A cell that contains the recombinant DNA after transformation
Q.11 Which technique separates DNA fragments based on size?
Polymerase chain reaction (PCR)
Gel electrophoresis
Southern blotting
DNA sequencing
Explanation - Gel electrophoresis moves DNA fragments through a matrix under an electric field; smaller fragments travel faster.
Correct answer is: Gel electrophoresis
Q.12 What is the primary role of a “origin of replication (Ori)” in a plasmid?
To signal where transcription should start
To provide a site for DNA replication within the host
To encode a selectable marker
To bind restriction enzymes
Explanation - Ori is the sequence where host replication machinery initiates copying of the plasmid DNA.
Correct answer is: To provide a site for DNA replication within the host
Q.13 Which of the following is NOT a typical step in the construction of a recombinant DNA molecule?
Isolation of the gene of interest
Restriction digestion of vector and insert
Transformation of host cells
Transcription of the plasmid DNA into mRNA
Explanation - Transcription occurs after the recombinant plasmid is inside the host and is not part of the cloning construction steps.
Correct answer is: Transcription of the plasmid DNA into mRNA
Q.14 In the polymerase chain reaction (PCR), what is the function of the “annealing” step?
Denature the double‑stranded DNA
Synthesize new DNA strands
Allow primers to bind to the target sequence
Separate the reaction mixture into fractions
Explanation - During annealing, the temperature is lowered so that short primers hybridize to complementary sites on the template DNA.
Correct answer is: Allow primers to bind to the target sequence
Q.15 A “shuttle vector” is designed to replicate in:
Two different host species
Only in yeast cells
Only in bacterial cells
Only in mammalian cells
Explanation - Shuttle vectors contain origins of replication for two distinct organisms, allowing DNA transfer between them.
Correct answer is: Two different host species
Q.16 Which of the following is a potential risk associated with recombinant DNA technology?
Spontaneous generation of new species
Uncontrolled replication of inserted genes in the environment
Immediate cure of all genetic diseases
Elimination of antibiotic resistance in bacteria
Explanation - If recombinant organisms escape containment, they could spread engineered traits, raising ecological and biosafety concerns.
Correct answer is: Uncontrolled replication of inserted genes in the environment
Q.17 Which of the following statements about the CRISPR‑Cas9 system is correct?
It uses restriction enzymes to cut DNA.
It requires a guide RNA to target specific DNA sequences.
It can only delete DNA, not insert it.
It works exclusively in prokaryotes.
Explanation - CRISPR‑Cas9 uses a short guide RNA that pairs with the target DNA, directing Cas9 to introduce a double‑strand break.
Correct answer is: It requires a guide RNA to target specific DNA sequences.
Q.18 In recombinant DNA technology, a “fusion protein” is created by:
Linking two genes in the same reading frame
Fusing two plasmids together
Joining two different proteins after translation
Cross‑linking proteins with chemical agents
Explanation - Fusion proteins are expressed when two coding sequences are placed consecutively, producing a single polypeptide with combined functions.
Correct answer is: Linking two genes in the same reading frame
Q.19 What does the term “transformation” refer to in bacterial genetics?
The process of bacterial conjugation
Uptake of naked DNA from the environment
Infection by a bacteriophage
Division of bacterial cells
Explanation - Transformation is the uptake and incorporation of extracellular DNA by a bacterial cell.
Correct answer is: Uptake of naked DNA from the environment
Q.20 Which of these vectors can accommodate the largest DNA inserts?
Plasmid
Bacterial artificial chromosome (BAC)
Cosmid
Phage λ
Explanation - BACs can carry inserts of up to 300 kb, larger than plasmids, cosmids, or lambda phage vectors.
Correct answer is: Bacterial artificial chromosome (BAC)
Q.21 The “blue‑white screening” method is used to identify:
Successful ligation of an insert into a plasmid
Presence of antibiotic resistance
Plasmids that replicate in yeast
Correct orientation of an insert
Explanation - Insertion of a DNA fragment disrupts the lacZ α‑fragment, producing white colonies; blue colonies retain functional β‑galactosidase.
Correct answer is: Successful ligation of an insert into a plasmid
Q.22 What is the main advantage of using a “high‑copy number plasmid” as a vector?
It integrates into the host chromosome
It yields large amounts of recombinant DNA per cell
It confers resistance to multiple antibiotics
It cannot be transferred to other bacteria
Explanation - High‑copy plasmids replicate many times per cell cycle, increasing the yield of the cloned gene.
Correct answer is: It yields large amounts of recombinant DNA per cell
Q.23 Which enzyme is used to amplify a specific DNA segment in vitro?
RNA polymerase
DNA ligase
DNA polymerase I
Taq DNA polymerase
Explanation - Taq polymerase, derived from Thermus aquaticus, is heat‑stable and used in PCR to synthesize DNA.
Correct answer is: Taq DNA polymerase
Q.24 In a recombinant protein expression system, a “His‑tag” is used for:
Enhancing transcriptional activity
Facilitating protein purification via metal affinity chromatography
Increasing protein solubility
Targeting the protein to the nucleus
Explanation - A poly‑histidine tag binds nickel or cobalt ions, allowing selective purification of the tagged protein.
Correct answer is: Facilitating protein purification via metal affinity chromatography
Q.25 Which of the following best describes the term “gene gun”?
A device that uses electrical pulses to lyse cells
A method to deliver DNA into plant cells via high‑velocity microparticles
An apparatus for sequencing DNA
A tool for measuring gene expression levels
Explanation - The gene gun (biolistic particle delivery) propels DNA‑coated metal particles into plant tissue for transformation.
Correct answer is: A method to deliver DNA into plant cells via high‑velocity microparticles
Q.26 Which of the following is a common selectable marker used in eukaryotic cell culture?
Kanamycin resistance
Neomycin (G418) resistance
Ampicillin resistance
Tetracycline resistance
Explanation - G418 selects for eukaryotic cells that have incorporated the neomycin resistance gene, allowing survival in the presence of the drug.
Correct answer is: Neomycin (G418) resistance
Q.27 The process of moving a recombinant plasmid from one bacterial species to another via direct contact is called:
Transformation
Conjugation
Transduction
Transfection
Explanation - Conjugation involves a pilus-mediated transfer of plasmids between bacterial cells.
Correct answer is: Conjugation
Q.28 What does the term “codon optimization” refer to in recombinant protein production?
Changing the protein’s amino‑acid sequence for higher activity
Altering the DNA sequence to match the host’s preferred codon usage
Removing introns from a eukaryotic gene
Adding a signal peptide for secretion
Explanation - Codon optimization modifies the gene without changing the protein, improving translation efficiency in the host organism.
Correct answer is: Altering the DNA sequence to match the host’s preferred codon usage
Q.29 Which of the following statements about “site‑directed mutagenesis” is true?
It introduces random mutations throughout the genome.
It uses CRISPR to delete entire genes.
It allows specific nucleotide changes at predetermined locations.
It can only be performed in viral vectors.
Explanation - Site‑directed mutagenesis uses primers containing desired mutations to create precise changes in the DNA sequence.
Correct answer is: It allows specific nucleotide changes at predetermined locations.
Q.30 Which of the following is the most common method for introducing plasmid DNA into mammalian cells?
Electroporation
Heat shock
Chemical transformation using calcium chloride
Phage infection
Explanation - Electroporation applies an electric field to create temporary pores in the cell membrane, allowing plasmid uptake in mammalian cells.
Correct answer is: Electroporation
Q.31 In a recombinant DNA construct, the “terminator” sequence is required to:
Initiate transcription
Terminate transcription and release the mRNA
Enhance translation efficiency
Provide antibiotic resistance
Explanation - Terminators signal RNA polymerase to stop transcription, ensuring proper mRNA processing.
Correct answer is: Terminate transcription and release the mRNA
Q.32 Which of the following best explains why a “low‑copy number plasmid” might be preferred for cloning toxic genes?
It replicates more quickly than high‑copy plasmids.
It reduces the metabolic burden on the host cell.
It integrates into the host chromosome.
It provides stronger promoter activity.
Explanation - Low‑copy plasmids limit the amount of toxic protein expressed, helping the host survive.
Correct answer is: It reduces the metabolic burden on the host cell.
Q.33 The “pUC” series of plasmids contain the lacZα fragment for which purpose?
Blue‑white screening
Antibiotic resistance
Origin of replication
Promoter activity
Explanation - The lacZα fragment restores β‑galactosidase activity unless disrupted by an inserted fragment, enabling colony color screening.
Correct answer is: Blue‑white screening
Q.34 Which of the following is NOT a typical feature of a mammalian expression vector?
CMV promoter
SV40 polyadenylation signal
Bacterial origin of replication
Operon for polycistronic expression
Explanation - Mammalian cells generally do not use operons; each gene is usually driven by its own promoter.
Correct answer is: Operon for polycistronic expression
Q.35 A “reporter gene” is used in recombinant DNA experiments primarily to:
Provide antibiotic resistance
Enable visualization or quantification of gene expression
Facilitate DNA replication
Induce cell death
Explanation - Reporter genes (e.g., GFP, luciferase) produce measurable signals that indicate the activity of regulatory elements.
Correct answer is: Enable visualization or quantification of gene expression
Q.36 Which of the following enzymes is most suitable for creating blunt‑ended DNA fragments?
EcoRI
HindIII
SmaI
BamHI
Explanation - SmaI cuts DNA at a palindromic site producing blunt ends, whereas EcoRI, HindIII, and BamHI generate sticky ends.
Correct answer is: SmaI
Q.37 What is the purpose of a “poly‑A tail” in eukaryotic mRNA produced from a recombinant construct?
To initiate transcription
To signal termination of transcription
To enhance mRNA stability and translation
To facilitate nuclear export
Explanation - The poly‑A tail protects mRNA from degradation and aids ribosome recruitment for translation.
Correct answer is: To enhance mRNA stability and translation
Q.38 In the context of recombinant DNA, what does the acronym “GMO” stand for?
Genetically Modified Organism
Gene Mapping Operation
Global Molecular Optimizer
Genomic Mutation Organizer
Explanation - GMO refers to an organism whose genetic material has been altered using recombinant DNA technology.
Correct answer is: Genetically Modified Organism
Q.39 Which of the following is an example of a “synthetic biology” application using recombinant DNA?
Cloning a gene into a plasmid
Sequencing a genome
Designing a genetic circuit that produces a biosensor
Using PCR to amplify DNA
Explanation - Synthetic biology engineers novel biological systems, such as biosensors, by assembling DNA parts into functional circuits.
Correct answer is: Designing a genetic circuit that produces a biosensor
Q.40 Which of the following is a key difference between a plasmid and a viral vector?
Plasmids can replicate in eukaryotic cells without integration.
Viral vectors cannot carry large DNA fragments.
Plasmids always integrate into the host genome.
Viral vectors are typically non‑infectious.
Explanation - Plasmids generally remain episomal, while many viral vectors either integrate or rely on viral replication mechanisms.
Correct answer is: Plasmids can replicate in eukaryotic cells without integration.
Q.41 Which of the following best describes the function of “RNA polymerase II” in eukaryotic recombinant expression systems?
Synthesizes tRNA molecules
Transcribes ribosomal RNA (rRNA)
Transcribes messenger RNA (mRNA)
Replicates DNA
Explanation - RNA polymerase II is responsible for the transcription of protein‑coding genes into mRNA.
Correct answer is: Transcribes messenger RNA (mRNA)
Q.42 In a recombinant construct, an “IRES” element is used to:
Initiate transcription
Allow translation of two open reading frames from a single mRNA
Terminate translation
Increase plasmid copy number
Explanation - Internal Ribosome Entry Sites (IRES) enable ribosomes to bind internally, permitting bicistronic expression.
Correct answer is: Allow translation of two open reading frames from a single mRNA
Q.43 Which of the following is the most common method to verify that a DNA insert is present in a plasmid?
Northern blotting
DNA sequencing
Western blotting
Chromatin immunoprecipitation
Explanation - Sequencing confirms the identity and orientation of the inserted DNA fragment.
Correct answer is: DNA sequencing
Q.44 A “phagemid” is a hybrid vector that combines features of:
Plasmid and bacteriophage
Cosmid and yeast artificial chromosome
BAC and viral vector
Plasmid and mitochondrial DNA
Explanation - Phagemids contain a plasmid origin of replication and phage packaging signals, enabling both replication and phage-mediated infection.
Correct answer is: Plasmid and bacteriophage
Q.45 The process of “electroporation” primarily relies on:
Heat shock to open pores
Chemical treatment with calcium chloride
High-voltage electric pulses to transiently permeabilize membranes
Viral infection
Explanation - Electric pulses create temporary pores in cell membranes, allowing DNA to enter the cell.
Correct answer is: High-voltage electric pulses to transiently permeabilize membranes
Q.46 In recombinant DNA technology, which of the following is a “binary vector” used for?
Agrobacterium‑mediated plant transformation
Bacterial conjugation
Phage display
RNA interference
Explanation - Binary vectors have a T‑DNA region for plant integration and a separate backbone for replication in Agrobacterium.
Correct answer is: Agrobacterium‑mediated plant transformation
Q.47 Which of the following is an advantage of using a “synthetic promoter” in recombinant constructs?
It can be designed to respond to specific stimuli
It reduces plasmid size dramatically
It eliminates the need for a selectable marker
It always yields higher protein expression
Explanation - Synthetic promoters can be engineered to be inducible or tissue‑specific, providing precise control of gene expression.
Correct answer is: It can be designed to respond to specific stimuli
Q.48 What does the term “in vitro transcription” refer to?
Transcribing DNA inside living cells
Synthesizing RNA from a DNA template in a test tube
Transcribing RNA into DNA
Cloning DNA fragments in bacteria
Explanation - In vitro transcription uses RNA polymerase and a DNA template to produce RNA outside of cells.
Correct answer is: Synthesizing RNA from a DNA template in a test tube
Q.49 The “T7 promoter” is most commonly used in recombinant systems to:
Drive high‑level expression in bacterial cells using T7 RNA polymerase
Provide antibiotic resistance
Enable replication in yeast
Terminate transcription
Explanation - The T7 promoter is recognized by T7 RNA polymerase, leading to strong transcription of downstream genes in specialized host strains.
Correct answer is: Drive high‑level expression in bacterial cells using T7 RNA polymerase
Q.50 Which of the following best describes the purpose of a “spacer” sequence in a CRISPR guide RNA?
To bind the Cas9 protein
To provide a scaffold for Cas9 cleavage
To prevent off‑target effects
To encode a fluorescent protein
Explanation - The spacer (or guide) region of the gRNA is complementary to the target DNA, directing Cas9 to the correct site.
Correct answer is: To provide a scaffold for Cas9 cleavage
Q.51 Which of the following is an example of a “non‑homologous end joining (NHEJ)” outcome after a CRISPR‑induced double‑strand break?
Precise insertion of a donor template
Deletion or insertion of a few base pairs at the cut site
Replacement of an entire gene
Integration of a viral genome
Explanation - NHEJ repairs DSBs by ligating ends directly, often introducing small indels that can disrupt gene function.
Correct answer is: Deletion or insertion of a few base pairs at the cut site
Q.52 When constructing a recombinant protein that needs to be secreted, which DNA element is essential?
A strong terminator
A signal peptide coding sequence
An origin of replication
A selectable marker
Explanation - Signal peptides direct the nascent protein to the secretory pathway, enabling secretion out of the cell.
Correct answer is: A signal peptide coding sequence
Q.53 Which of the following methods can be used to generate a library of random DNA fragments for screening?
Site‑directed mutagenesis
Error‑prone PCR
Southern blotting
Northern blotting
Explanation - Error‑prone PCR introduces random mutations during amplification, creating diverse variant libraries.
Correct answer is: Error‑prone PCR
Q.54 The “pBR322” plasmid was historically important because it was the first:
Plasmid with an antibiotic resistance gene
Plasmid to be sequenced completely
Plasmid containing a multiple cloning site
Plasmid used for protein expression
Explanation - pBR322 carries both ampicillin and tetracycline resistance genes, enabling selectable markers for cloning.
Correct answer is: Plasmid with an antibiotic resistance gene
Q.55 Which of the following is the correct order of steps in a typical recombinant DNA cloning workflow?
Transformation → Ligation → Restriction digestion → PCR
PCR → Restriction digestion → Ligation → Transformation
Ligation → PCR → Transformation → Restriction digestion
Transformation → PCR → Ligation → Restriction digestion
Explanation - First amplify the gene (PCR), cut vector and insert (restriction), join (ligation), then introduce into host (transformation).
Correct answer is: PCR → Restriction digestion → Ligation → Transformation
Q.56 What is the role of a “ribosome binding site (RBS)” in a prokaryotic expression vector?
To start DNA replication
To recruit ribosomes for translation initiation
To terminate transcription
To confer antibiotic resistance
Explanation - The RBS (Shine‑Dalgarno sequence) aligns the ribosome with the start codon for efficient translation.
Correct answer is: To recruit ribosomes for translation initiation
Q.57 Which of the following best describes a “knock‑out” mouse?
A mouse that overexpresses a target gene
A mouse in which a specific gene has been deleted or disrupted
A mouse that carries a viral vector
A mouse that is resistant to antibiotics
Explanation - Gene knock‑out mice are generated by replacing or disrupting a target gene, often using homologous recombination or CRISPR.
Correct answer is: A mouse in which a specific gene has been deleted or disrupted
Q.58 In recombinant DNA technology, what does the term “heterologous expression” refer to?
Expression of a gene in its native organism
Expression of a gene in a different host species
Expression of multiple genes from a single promoter
Expression of a gene without a promoter
Explanation - Heterologous expression means producing a gene product in a non‑native host, such as human proteins in bacteria.
Correct answer is: Expression of a gene in a different host species
Q.59 Which of the following is a typical use of recombinant DNA technology in agriculture?
Producing synthetic fertilizers
Developing pest‑resistant crops
Increasing soil pH
Harvesting rainwater
Explanation - Genes conferring insect resistance (e.g., Bt toxin) are introduced into crops to reduce pesticide usage.
Correct answer is: Developing pest‑resistant crops
Q.60 What is the purpose of adding a “poly‑histidine tag” at the C‑terminus of a recombinant protein?
To improve protein folding
To increase transcription rate
To enable affinity purification using metal chelate columns
To target the protein to the nucleus
Explanation - His‑tags bind nickel or cobalt ions, allowing easy purification via immobilized metal affinity chromatography (IMAC).
Correct answer is: To enable affinity purification using metal chelate columns
Q.61 Which of the following is a characteristic of a “cosmid” vector?
It can replicate in mammalian cells without a promoter.
It contains a λ phage cos site allowing packaging of large inserts.
It integrates into the host genome at a specific locus.
It is derived from mitochondrial DNA.
Explanation - Cosmids combine plasmid replication functions with λ phage cos sites, enabling cloning of DNA fragments up to ~45 kb.
Correct answer is: It contains a λ phage cos site allowing packaging of large inserts.
Q.62 In the context of recombinant DNA, what does the term “operon” specifically describe?
A group of genes transcribed together from a single promoter in prokaryotes
A type of viral vector
A DNA sequence that terminates transcription
A DNA repair pathway
Explanation - Operons enable coordinated expression of functionally related genes in bacteria.
Correct answer is: A group of genes transcribed together from a single promoter in prokaryotes
Q.63 Which of the following best explains why “heat shock” is used during bacterial transformation?
It increases the permeability of the cell wall allowing DNA entry.
It kills non‑transformed cells.
It activates restriction enzymes inside the cell.
It induces plasmid replication.
Explanation - A brief heat shock creates a thermal imbalance that facilitates DNA uptake through the bacterial membrane.
Correct answer is: It increases the permeability of the cell wall allowing DNA entry.
Q.64 Which of the following enzymes is essential for repairing nicks in the DNA backbone after ligation?
DNA polymerase
RNA polymerase
DNA ligase
Helicase
Explanation - DNA ligase forms phosphodiester bonds between adjacent nucleotides, sealing nicks created during cloning.
Correct answer is: DNA ligase
Q.65 The “pUC19” plasmid contains which antibiotic resistance gene?
Kanamycin
Ampicillin
Chloramphenicol
Tetracycline
Explanation - pUC19 carries the β‑lactamase gene conferring resistance to ampicillin, used for selection of transformed cells.
Correct answer is: Ampicillin
Q.66 What is the primary function of a “terminator” sequence in a bacterial plasmid?
Initiate DNA replication
Terminate transcription of the downstream gene
Provide a binding site for RNA polymerase
Encode a selectable marker
Explanation - Terminator sequences signal RNA polymerase to stop transcription, ensuring proper mRNA processing.
Correct answer is: Terminate transcription of the downstream gene
Q.67 Which of the following is NOT a typical characteristic of a “viral vector” used for gene therapy?
Ability to infect dividing and non‑dividing cells
High packaging capacity for large DNA fragments
Self‑replication without a host genome
Potential for immune response
Explanation - Viral vectors generally lack essential replication genes, preventing autonomous replication without a helper system.
Correct answer is: Self‑replication without a host genome
Q.68 In recombinant DNA technology, the “polymerase chain reaction” (PCR) is primarily used to:
Separate DNA fragments by size
Amplify a specific DNA segment exponentially
Introduce mutations into a gene
Translate RNA into protein
Explanation - PCR uses repeated cycles of denaturation, annealing, and extension to generate millions of copies of a target DNA region.
Correct answer is: Amplify a specific DNA segment exponentially
Q.69 Which of the following statements about “gene silencing” using RNA interference (RNAi) is true?
It permanently deletes the target gene.
It uses short double‑stranded RNA to degrade complementary mRNA.
It enhances transcription of the target gene.
It requires integration of a viral vector.
Explanation - RNAi employs siRNA or shRNA to guide the RISC complex to cleave matching mRNA, reducing protein expression.
Correct answer is: It uses short double‑stranded RNA to degrade complementary mRNA.
Q.70 Which of the following is a common method to confirm the orientation of an insert in a plasmid?
Restriction digestion analysis
Southern blotting
Western blotting
ELISA
Explanation - Digesting the plasmid with specific enzymes and analyzing fragment sizes by gel electrophoresis reveals insert orientation.
Correct answer is: Restriction digestion analysis
Q.71 A “synthetic gene” designed for expression in yeast would most likely be optimized for:
High GC content
Yeast codon usage bias
Prokaryotic ribosome binding sites
Bacterial promoters
Explanation - Optimizing codons to match the host's tRNA abundance improves translation efficiency in yeast.
Correct answer is: Yeast codon usage bias
Q.72 Which of the following is a characteristic feature of a “BAC” (Bacterial Artificial Chromosome) vector?
It integrates into the host chromosome automatically.
It can carry inserts up to 300 kb.
It replicates only in yeast cells.
It contains a viral capsid.
Explanation - BACs are designed for stable maintenance of large DNA fragments (up to several hundred kilobases) in bacterial cells.
Correct answer is: It can carry inserts up to 300 kb.
Q.73 In recombinant DNA cloning, the “vector backbone” typically contains:
The gene of interest only
Only the promoter region
Elements needed for replication and selection
A fluorescent reporter gene
Explanation - The backbone provides the origin of replication, selectable marker, and sometimes promoter elements.
Correct answer is: Elements needed for replication and selection
Q.74 Which of the following best explains why an “inducible promoter” is used in some expression vectors?
To permanently turn on gene expression
To control the timing and level of gene expression with an external stimulus
To increase plasmid copy number
To provide antibiotic resistance
Explanation - Inducible promoters (e.g., lac, arabinose) allow researchers to turn gene expression on or off by adding specific chemicals.
Correct answer is: To control the timing and level of gene expression with an external stimulus
Q.75 The “Golden Gate” cloning method relies on which type of restriction enzymes?
Type I enzymes
Type II enzymes that generate blunt ends
Type IIs enzymes that cut outside their recognition site
Type III enzymes
Explanation - Type IIs enzymes create custom overhangs, enabling scar‑less assembly of multiple DNA fragments in a single reaction.
Correct answer is: Type IIs enzymes that cut outside their recognition site
Q.76 Which of the following is a major ethical concern associated with creating genetically modified humans using recombinant DNA technology?
Increased crop yield
Potential off‑target effects and societal inequality
Enhanced bacterial growth rates
Improved vaccine production
Explanation - Human germline editing raises concerns about unintended mutations, consent, and creating genetic disparities.
Correct answer is: Potential off‑target effects and societal inequality
Q.77 What does the term “synthetic promoter” imply in recombinant DNA design?
A promoter taken from a virus
A promoter engineered from basic DNA elements to achieve desired strength or regulation
A promoter that cannot be recognized by any RNA polymerase
A promoter that automatically replicates the plasmid
Explanation - Synthetic promoters are custom-built sequences that provide tailored transcriptional control.
Correct answer is: A promoter engineered from basic DNA elements to achieve desired strength or regulation
Q.78 In a recombinant DNA experiment, the presence of “sticky ends” after restriction digestion facilitates:
Random ligation of any DNA fragments
Specific and efficient ligation of compatible DNA fragments
Immediate transcription of the DNA
Replication of the DNA without a polymerase
Explanation - Sticky ends have complementary overhangs that anneal, guiding ligase to join the fragments correctly.
Correct answer is: Specific and efficient ligation of compatible DNA fragments
Q.79 Which of the following statements about “homologous recombination” in gene targeting is correct?
It only occurs in prokaryotes.
It allows precise insertion or replacement of DNA at a specific genomic locus.
It always results in random integration of DNA.
It is independent of sequence similarity.
Explanation - Homologous recombination uses sequence homology to exchange DNA at defined genomic locations, enabling targeted gene editing.
Correct answer is: It allows precise insertion or replacement of DNA at a specific genomic locus.
Q.80 What is the purpose of adding a “KpnI” site to the 5' end of a PCR primer?
To increase primer melting temperature
To create a restriction site for cloning the amplified fragment
To act as a transcription terminator
To bind to the DNA polymerase
Explanation - Including a restriction site in the primer allows the PCR product to be digested and ligated into a vector at that site.
Correct answer is: To create a restriction site for cloning the amplified fragment
Q.81 Which of the following best describes “phage display” technology?
Using bacteriophages to amplify DNA fragments
Expressing peptide or protein libraries on the surface of bacteriophages for selection
Transducing eukaryotic cells with viral vectors
Sequencing the phage genome
Explanation - Phage display links genotype and phenotype, allowing selection of binding molecules from large libraries.
Correct answer is: Expressing peptide or protein libraries on the surface of bacteriophages for selection
Q.82 In the context of recombinant DNA, a “fusion tag” can be used for:
Enhancing gene transcription
Facilitating protein solubility, purification, or detection
Increasing plasmid copy number
Preventing DNA methylation
Explanation - Fusion tags (e.g., GST, MBP, FLAG) aid in protein handling and downstream applications.
Correct answer is: Facilitating protein solubility, purification, or detection
Q.83 Which of the following is an example of a “reporter assay” used to test promoter activity?
Measuring β‑galactosidase activity from a lacZ reporter gene
Assessing antibiotic resistance growth curves
Quantifying plasmid copy number by qPCR
Detecting DNA methylation by bisulfite sequencing
Explanation - β‑galactosidase activity provides a quantitative read‑out of promoter-driven transcription.
Correct answer is: Measuring β‑galactosidase activity from a lacZ reporter gene
Q.84 When designing a recombinant construct for secreted protein production in mammalian cells, which signal peptide is commonly used?
T7 promoter
SV40 polyadenylation signal
IgG κ-chain leader sequence
Lac operon operator
Explanation - The IgG κ‑chain leader directs nascent proteins into the secretory pathway in mammalian cells.
Correct answer is: IgG κ-chain leader sequence
Q.85 Which of the following is the most appropriate method to introduce a large DNA fragment (>100 kb) into a bacterial host?
Transformation with a standard plasmid
Electroporation of a cosmid
Transduction with a bacteriophage λ
Conjugation using a BAC
Explanation - BACs can carry large inserts and are efficiently transferred by bacterial conjugation.
Correct answer is: Conjugation using a BAC
Q.86 What is the purpose of adding a “stop codon” immediately after a coding sequence in a recombinant vector?
To start transcription
To terminate translation and release the polypeptide
To enhance DNA replication
To provide antibiotic resistance
Explanation - A stop codon signals ribosomes to end translation, preventing read‑through into downstream sequences.
Correct answer is: To terminate translation and release the polypeptide
Q.87 Which of the following technologies allows precise insertion of a gene at a specific “safe harbor” locus in the human genome?
Random integration via plasmid transfection
CRISPR‑Cas9 mediated homology‑directed repair
Electroporation without a donor template
RNA interference
Explanation - HDR with CRISPR can insert a donor DNA precisely at chosen genomic sites, such as the AAVS1 safe harbor.
Correct answer is: CRISPR‑Cas9 mediated homology‑directed repair
Q.88 The “pGEX” series of vectors is specifically designed for expression of proteins fused to:
Glutathione S‑transferase (GST)
Maltose‑binding protein (MBP)
His‑tag
Flag tag
Explanation - pGEX vectors produce GST‑fusion proteins, which can be purified using glutathione affinity chromatography.
Correct answer is: Glutathione S‑transferase (GST)
Q.89 Which of the following best describes a “self‑splicing intron” used in some recombinant constructs?
An intron that requires the spliceosome for removal
An intron that can excise itself from RNA without additional proteins
An intron that encodes antibiotic resistance
An intron that enhances transcription
Explanation - Group I introns can self‑splice, allowing precise removal of the intron from the transcribed RNA.
Correct answer is: An intron that can excise itself from RNA without additional proteins
Q.90 In recombinant DNA work, why is it important to use a “low‑temperature” DNA ligase for blunt‑end ligations?
Low temperature increases ligase activity on blunt ends
Low temperature prevents DNA denaturation
Low temperature reduces the rate of unwanted side reactions
Low temperature improves restriction enzyme activity
Explanation - Blunt‑end ligations are inefficient; low temperatures (e.g., 16 °C) enhance ligase binding and activity on blunt ends.
Correct answer is: Low temperature increases ligase activity on blunt ends
Q.91 Which of the following statements about “gene drives” created with recombinant DNA is accurate?
They only work in bacterial populations.
They bias inheritance to spread a genetic trait through a population rapidly.
They permanently delete the targeted gene.
They require antibiotics to function.
Explanation - Gene drives use CRISPR or other mechanisms to ensure a genetic element is transmitted to >50% of offspring, overriding Mendelian inheritance.
Correct answer is: They bias inheritance to spread a genetic trait through a population rapidly.
Q.92 Which of the following is a common method for delivering recombinant DNA into plant cells?
Electroporation of leaf discs
Agrobacterium‑mediated transformation
Microinjection into the nucleus
Viral transduction using lentivirus
Explanation - Agrobacterium transfers T‑DNA into plant genomes, a widely used method for stable genetic modification of plants.
Correct answer is: Agrobacterium‑mediated transformation
Q.93 Which of the following best explains why “codon bias” can affect protein expression in heterologous hosts?
Different organisms have varying tRNA abundances for specific codons.
Codon bias changes the DNA melting temperature.
Codon bias determines the location of the promoter.
Codon bias only affects transcription, not translation.
Explanation - If a gene uses rare codons for the host, translation can stall; optimizing codons to match host tRNA pools improves expression.
Correct answer is: Different organisms have varying tRNA abundances for specific codons.
Q.94 In the context of recombinant DNA, a “mini‑gene” typically refers to:
A very short plasmid without an origin of replication
A synthetic construct containing only essential regulatory elements and a coding sequence
A gene that encodes a small peptide
A fragment of DNA that cannot be expressed
Explanation - Mini‑genes are compact designs that include promoter, coding region, and terminator, used for streamlined expression.
Correct answer is: A synthetic construct containing only essential regulatory elements and a coding sequence
Q.95 Which of the following is an example of an “insulator” element used in recombinant constructs?
The SV40 origin of replication
The chicken β‑globin HS4 insulator
The lac operon operator
The CMV promoter
Explanation - Insulators like HS4 block the influence of neighboring enhancers or silencers, stabilizing transgene expression.
Correct answer is: The chicken β‑globin HS4 insulator
Q.96 Which of the following describes a “knock‑in” strategy in recombinant DNA research?
Insertion of a foreign gene at a specific genomic locus
Deletion of a target gene
Random integration of plasmid DNA
Overexpression of an endogenous gene
Explanation - Knock‑in replaces or adds a gene at a precise site, often using homologous recombination or CRISPR HDR.
Correct answer is: Insertion of a foreign gene at a specific genomic locus
Q.97 The “pET” series of vectors is primarily used for:
Expression of recombinant proteins in E. coli under the T7 promoter
Cloning of large genomic fragments in yeast
Stable integration into mammalian chromosomes
RNA interference studies in plants
Explanation - pET vectors contain a T7 promoter and are designed for high‑level protein production in BL21(DE3) strains.
Correct answer is: Expression of recombinant proteins in E. coli under the T7 promoter
Q.98 Which of the following is a main advantage of using a “split‑intein” system for protein splicing in recombinant expression?
It eliminates the need for a promoter.
It allows post‑translational ligation of two separate polypeptide fragments.
It reduces the size of the plasmid dramatically.
It automatically transports proteins into the nucleus.
Explanation - Split inteins catalyze protein trans‑splicing, joining two separate proteins into a single functional polypeptide after translation.
Correct answer is: It allows post‑translational ligation of two separate polypeptide fragments.
Q.99 In recombinant DNA technology, the term “vector” most accurately refers to:
Any DNA molecule used to carry foreign DNA into a host cell
A protein that binds DNA
A lipid vesicle used for drug delivery
A sequence that codes for a fluorescent protein
Explanation - Vectors are DNA carriers such as plasmids, phages, cosmids, or viral genomes used to deliver genetic material.
Correct answer is: Any DNA molecule used to carry foreign DNA into a host cell
Q.100 Which of the following is an example of a “selection marker” that allows growth of transformed yeast cells?
URA3 gene (uracil prototrophy)
Ampicillin resistance
Kanamycin resistance
G418 resistance
Explanation - URA3 complements uracil auxotrophy, enabling selection of yeast transformants on uracil‑deficient media.
Correct answer is: URA3 gene (uracil prototrophy)
Q.101 Which of the following best describes the purpose of a “poly‑adenylation signal” in a mammalian expression cassette?
To initiate DNA replication
To signal termination and poly‑A tail addition to the mRNA
To enhance ribosome binding
To provide antibiotic resistance
Explanation - The poly‑A signal (e.g., SV40 poly‑A) directs cleavage and polyadenylation of the nascent transcript, stabilizing mRNA.
Correct answer is: To signal termination and poly‑A tail addition to the mRNA
Q.102 Which of the following is a typical advantage of using a “baculovirus” expression system?
Low‑cost production in bacteria
High‑level expression of properly folded eukaryotic proteins in insect cells
Integration into the human genome
Direct delivery of DNA into plant chloroplasts
Explanation - Baculovirus vectors infect insect cells, providing post‑translational modifications and high protein yields.
Correct answer is: High‑level expression of properly folded eukaryotic proteins in insect cells
Q.103 A recombinant plasmid designed to express a fluorescent protein in mammalian cells should contain:
A bacterial origin of replication only
A eukaryotic promoter, Kozak sequence, and poly‑A signal
A chloroplast targeting peptide
A prokaryotic ribosome binding site
Explanation - Eukaryotic expression requires a promoter (e.g., CMV), a Kozak consensus for translation initiation, and a poly‑A tail signal.
Correct answer is: A eukaryotic promoter, Kozak sequence, and poly‑A signal
Q.104 Which of the following is a common method to generate a “single‑strand DNA” template for in vitro transcription?
PCR using a 5'‑phosphorylated primer and lambda exonuclease digestion
Restriction digestion with EcoRI
Ligation of two double‑stranded fragments
Gel electrophoresis of double‑stranded DNA
Explanation - Lambda exonuclease digests the 5'‑phosphorylated strand, leaving a single‑strand DNA template for transcription.
Correct answer is: PCR using a 5'‑phosphorylated primer and lambda exonuclease digestion
Q.105 The “pMAL” vector series is engineered to produce proteins fused with:
Maltose‑binding protein (MBP)
Glutathione S‑transferase (GST)
His‑tag
Flag tag
Explanation - pMAL vectors generate MBP‑fusion proteins, facilitating solubility and affinity purification using amylose resin.
Correct answer is: Maltose‑binding protein (MBP)
Q.106 In recombinant DNA work, which of the following best explains why “heat‑shock” is combined with “calcium chloride” treatment of E. coli cells?
Calcium chloride stabilizes the plasmid, while heat‑shock opens the cell wall.
Calcium ions increase cell membrane permeability; heat‑shock drives DNA uptake.
Heat‑shock deactivates restriction enzymes; calcium chloride provides nutrients.
Both steps are required to lyse the cells for DNA extraction.
Explanation - CaCl₂ makes the membrane more permeable; a brief heat‑shock creates a thermal imbalance that facilitates DNA entry.
Correct answer is: Calcium ions increase cell membrane permeability; heat‑shock drives DNA uptake.
Q.107 Which of the following is a major reason to use a “low‑copy number plasmid” when cloning toxic genes?
To ensure rapid plasmid replication
To minimize the metabolic burden and reduce toxic protein levels
To increase the number of selectable markers
To enhance promoter strength
Explanation - Low‑copy plasmids limit expression of toxic products, helping the host survive.
Correct answer is: To minimize the metabolic burden and reduce toxic protein levels
Q.108 In a recombinant construct, the “Kozak sequence” is important for:
DNA replication
Transcription termination
Efficient translation initiation in eukaryotes
Antibiotic resistance
Explanation - The Kozak consensus (GCCACC AUG G) flanks the start codon, enhancing ribosome recognition and translation efficiency.
Correct answer is: Efficient translation initiation in eukaryotes
Q.109 Which of the following best defines “synthetic biology” in the context of recombinant DNA?
Sequencing natural genomes
Designing and constructing new biological parts, devices, and systems not found in nature
Studying protein folding using X‑ray crystallography
Applying antibiotics to select for transformed cells
Explanation - Synthetic biology combines engineering principles with DNA assembly to create novel functions and pathways.
Correct answer is: Designing and constructing new biological parts, devices, and systems not found in nature
Q.110 Which of the following is a commonly used selectable marker for yeast that allows growth on media lacking histidine?
HIS3
KanR
AmpR
TetR
Explanation - HIS3 complements histidine auxotrophy, enabling selection of transformants on histidine‑deficient plates.
Correct answer is: HIS3
Q.111 A researcher wants to insert a gene into the mitochondrial genome of a plant. Which vector type is most suitable?
Plasmid vector
Mitochondrial targeting vector with a mitochondrial transit peptide
Cosmid vector
Bacterial artificial chromosome (BAC)
Explanation - Mitochondrial targeting sequences direct the encoded protein or DNA to the mitochondria, enabling mitochondrial genome manipulation.
Correct answer is: Mitochondrial targeting vector with a mitochondrial transit peptide
Q.112 Which of the following best describes the purpose of a “spacer” sequence in a synthetic gene cassette?
To separate functional modules and prevent unwanted secondary structures
To code for an extra peptide
To act as an antibiotic resistance gene
To initiate DNA replication
Explanation - Spacers provide physical distance and flexibility between parts, reducing interference and improving expression.
Correct answer is: To separate functional modules and prevent unwanted secondary structures
Q.113 Which of the following is an advantage of using “Golden Gate Assembly” over traditional restriction‑ligation cloning?
It can assemble multiple fragments in a defined order without scar sequences.
It requires no enzymes.
It only works with blunt ends.
It eliminates the need for a vector backbone.
Explanation - Golden Gate uses type IIs enzymes to generate custom overhangs, allowing seamless, one‑pot assembly of many parts.
Correct answer is: It can assemble multiple fragments in a defined order without scar sequences.
Q.114 In recombinant DNA technology, the term “transgene” refers to:
A gene that is naturally present in the host genome
A gene transferred from one organism to another
A gene that encodes a toxin
A gene that cannot be expressed
Explanation - A transgene is an exogenous gene introduced into a host genome via recombinant techniques.
Correct answer is: A gene transferred from one organism to another
Q.115 Which of the following statements about the “T7 RNA polymerase” system is correct?
It is a eukaryotic polymerase that functions in the nucleus.
It requires the T7 promoter for transcription and provides high specificity.
It is inhibited by IPTG.
It cannot transcribe DNA templates larger than 5 kb.
Explanation - T7 RNA polymerase recognizes only the T7 promoter, enabling strong, controllable transcription in engineered strains.
Correct answer is: It requires the T7 promoter for transcription and provides high specificity.
Q.116 The “pCMV” vector is widely used because it contains:
A strong viral promoter for high expression in mammalian cells
A bacterial origin of replication only
A chloroplast transit peptide
A yeast replication origin
Explanation - The CMV (cytomegalovirus) immediate‑early promoter drives robust transcription in a broad range of mammalian cell types.
Correct answer is: A strong viral promoter for high expression in mammalian cells
Q.117 Which of the following techniques is used to create a “knock‑out” of a specific gene in mouse embryonic stem cells?
CRISPR‑Cas9 induced double‑strand break with HDR
RNA interference (RNAi)
Random insertion of a plasmid
Transposon mutagenesis
Explanation - CRISPR creates a targeted DSB; providing a repair template without the gene leads to precise knockout via homology‑directed repair.
Correct answer is: CRISPR‑Cas9 induced double‑strand break with HDR
Q.118 In recombinant DNA constructs, an “IRES” element allows:
Simultaneous translation of two open reading frames from a single mRNA
Initiation of DNA replication
Termination of transcription
Integration of the vector into the genome
Explanation - IRES enables ribosomes to bind internally, facilitating bicistronic expression without a second promoter.
Correct answer is: Simultaneous translation of two open reading frames from a single mRNA
Q.119 Which of the following best describes a “phagemid”?
A hybrid vector that combines plasmid replication functions with a phage packaging signal
A plasmid that only replicates in yeast
A viral vector that integrates into the host genome
A linear DNA fragment used for transformation
Explanation - Phagemids can be maintained as plasmids in bacteria and packaged into phage particles for display or infection.
Correct answer is: A hybrid vector that combines plasmid replication functions with a phage packaging signal
Q.120 What is the main function of a “terminator” in a bacterial expression cassette?
To initiate transcription
To stop transcription and release the RNA polymerase
To provide a ribosome binding site
To confer antibiotic resistance
Explanation - Terminator sequences signal RNA polymerase to end transcription, ensuring proper mRNA length.
Correct answer is: To stop transcription and release the RNA polymerase
Q.121 Which of the following is a typical characteristic of a “cosmid” vector?
It can replicate in mammalian cells without a promoter
It contains a λ phage cos site for packaging large DNA inserts
It integrates into the host chromosome automatically
It is derived from mitochondrial DNA
Explanation - Cosmids combine plasmid replication with λ cos sites, enabling cloning of fragments up to ~45 kb.
Correct answer is: It contains a λ phage cos site for packaging large DNA inserts
Q.122 In recombinant DNA technology, a “reporter gene” such as GFP is used to:
Provide antibiotic resistance
Induce cell death
Monitor expression by visual fluorescence
Catalyze DNA replication
Explanation - GFP emits green fluorescence when expressed, allowing direct observation of promoter activity or protein localization.
Correct answer is: Monitor expression by visual fluorescence
Q.123 Which of the following best explains why “codon optimization” is performed when expressing a bacterial gene in human cells?
To increase GC content for better stability
To match human codon usage, improving translation efficiency
To add a signal peptide for secretion
To insert introns for proper splicing
Explanation - Human cells have specific tRNA abundances; optimizing codons reduces translational pauses and boosts protein yield.
Correct answer is: To match human codon usage, improving translation efficiency
Q.124 Which of the following is a commonly used “selection marker” for bacterial transformation on agar plates?
Kanamycin resistance gene (KanR)
Green fluorescent protein (GFP)
β‑galactosidase (lacZ)
Neomycin phosphotransferase (NeoR)
Explanation - KanR provides resistance to kanamycin, allowing only transformed bacteria to grow on kanamycin‑containing media.
Correct answer is: Kanamycin resistance gene (KanR)
Q.125 In the context of recombinant DNA, what does “homology‑directed repair (HDR)” achieve?
Random integration of DNA
Precise insertion of a DNA template using sequence homology after a double‑strand break
Degradation of unwanted DNA fragments
Activation of the immune system
Explanation - HDR uses a donor DNA with homology arms to accurately repair CRISPR‑induced cuts, enabling precise genome editing.
Correct answer is: Precise insertion of a DNA template using sequence homology after a double‑strand break
Q.126 Which of the following is a key safety consideration when working with recombinant viruses?
Ensuring the virus can replicate indefinitely in any host
Removing all pathogenic genes and using replication‑deficient backbones
Using high concentrations of antibiotics to kill the virus
Avoiding any form of containment
Explanation - Safety guidelines require attenuation of viral vectors to prevent disease and uncontrolled spread.
Correct answer is: Removing all pathogenic genes and using replication‑deficient backbones
Q.127 Which of the following best describes a “synthetic operon” constructed using recombinant DNA techniques?
A natural bacterial operon cloned without modification
A designed cluster of genes with a common promoter, ribosome binding sites, and terminators
A single gene placed under multiple promoters
A viral genome inserted into a plasmid
Explanation - Synthetic operons mimic natural operons but are engineered to control multiple genes together in a custom way.
Correct answer is: A designed cluster of genes with a common promoter, ribosome binding sites, and terminators
Q.128 What is the role of “T4 DNA ligase” in the cloning process?
To cut DNA at specific sites
To join DNA fragments by forming phosphodiester bonds
To replicate DNA in vitro
To degrade RNA contaminants
Explanation - T4 DNA ligase catalyzes the formation of phosphodiester bonds between adjacent nucleotides, sealing nicks.
Correct answer is: To join DNA fragments by forming phosphodiester bonds
Q.129 Which of the following is a typical application of recombinant DNA technology in medicine?
Producing insulin in bacteria
Increasing crop yield through traditional breeding
Generating renewable energy from solar panels
Developing non‑genetic vaccines
Explanation - Recombinant human insulin expressed in E. coli revolutionized diabetes treatment.
Correct answer is: Producing insulin in bacteria