Q.1 What does the acronym PCR stand for in molecular biology?
Protein Chain Replication
Polymerase Chain Reaction
Photonic Catalytic Reaction
Partial Cell Recombination
Explanation - PCR (Polymerase Chain Reaction) is a technique used to amplify specific DNA fragments exponentially.
Correct answer is: Polymerase Chain Reaction
Q.2 Which enzyme is essential for the PCR process?
DNA ligase
RNA polymerase
Taq DNA polymerase
Reverse transcriptase
Explanation - Taq polymerase, derived from Thermus aquaticus, is heat‑stable and synthesizes DNA during PCR cycles.
Correct answer is: Taq DNA polymerase
Q.3 In environmental biotechnology, what is a biosensor primarily used for?
Generating electricity
Detecting specific contaminants
Culturing microbes
Measuring soil pH only
Explanation - Biosensors combine a biological recognition element (e.g., enzymes, DNA) with a transducer to detect pollutants such as heavy metals or organic compounds.
Correct answer is: Detecting specific contaminants
Q.4 Which of the following is a common vector used for cloning environmental DNA?
Plasmid
Ribosome
Mitochondrion
Chloroplast
Explanation - Plasmids are circular DNA molecules that can replicate independently and are widely used to clone and express foreign genes.
Correct answer is: Plasmid
Q.5 Metagenomics primarily studies:
Single-species genomes
The collective genome of microbial communities
Plant DNA only
Animal mitochondrial DNA
Explanation - Metagenomics bypasses the need for culturing by directly sequencing DNA extracted from environmental samples, revealing community composition and functional potential.
Correct answer is: The collective genome of microbial communities
Q.6 What is the main advantage of using CRISPR‑Cas9 in environmental biotechnology?
It can increase the temperature of reactors.
It enables precise editing of microbial genomes for enhanced pollutant degradation.
It produces electricity from sunlight.
It measures pH automatically.
Explanation - CRISPR‑Cas9 can be programmed to edit specific genes, allowing engineers to create microbes with improved capabilities for bioremediation.
Correct answer is: It enables precise editing of microbial genomes for enhanced pollutant degradation.
Q.7 Which technique is used to separate DNA fragments based on size?
Polymerase chain reaction
Gel electrophoresis
Northern blot
Western blot
Explanation - Gel electrophoresis applies an electric field to move negatively charged DNA through a gel matrix; smaller fragments migrate faster.
Correct answer is: Gel electrophoresis
Q.8 A gene that encodes for an enzyme capable of degrading toluene is introduced into a bacterium. This is an example of:
Biomagnification
Biostimulation
Bioaugmentation
Phytoextraction
Explanation - Bioaugmentation adds engineered microorganisms with desired catabolic pathways to a contaminated site to accelerate pollutant breakdown.
Correct answer is: Bioaugmentation
Q.9 Which of the following is NOT a typical component of a microbial biosensor?
Recognition element
Transducer
Amplifier circuit
Signal processor
Explanation - While electronic biosensors may include amplifiers, a basic biological biosensor consists of a recognition element (e.g., enzyme, DNA), a transducer, and a signal processor.
Correct answer is: Amplifier circuit
Q.10 In quantitative PCR (qPCR), fluorescence is measured to determine:
The temperature of the reaction
The amount of amplified DNA in real time
The pH of the sample
The protein content of cells
Explanation - qPCR uses fluorescent dyes or probes; the increase in fluorescence correlates with the accumulation of PCR product, allowing quantification.
Correct answer is: The amount of amplified DNA in real time
Q.11 Which of the following is a common selectable marker used in plasmid vectors for environmental biotech applications?
Kanamycin resistance gene
Green fluorescent protein (GFP)
Beta‑galactosidase (LacZ)
Luciferase
Explanation - Antibiotic resistance genes like kanamycin resistance allow researchers to select cells that have successfully taken up the plasmid.
Correct answer is: Kanamycin resistance gene
Q.12 Which sequencing technology provides the longest read lengths, useful for assembling complex environmental genomes?
Illumina short‑read sequencing
Sanger sequencing
Nanopore sequencing
Pyrosequencing
Explanation - Nanopore platforms can generate reads of tens to hundreds of kilobases, aiding assembly of metagenomic data from diverse microbes.
Correct answer is: Nanopore sequencing
Q.13 The term ‘bioprospecting’ in environmental biotechnology refers to:
Searching for fossils
Identifying and isolating useful genes or organisms from natural environments
Mining for metals
Measuring water flow
Explanation - Bioprospecting involves exploring ecosystems to discover novel enzymes, pathways, or organisms with potential industrial or environmental applications.
Correct answer is: Identifying and isolating useful genes or organisms from natural environments
Q.14 Which of the following is a widely used reporter gene for monitoring gene expression in engineered microbes?
lacZ
psbA
rbcL
psbD
Explanation - The lacZ gene encodes β‑galactosidase, which produces a detectable color change when substrate is added, indicating gene expression.
Correct answer is: lacZ
Q.15 When designing a synthetic pathway for mercury detoxification, which gene is commonly introduced into bacteria?
merA (mercuric reductase)
catA (catalase)
luxA (luciferase)
gfp (green fluorescent protein)
Explanation - merA encodes mercuric reductase, which reduces toxic Hg²⁺ to elemental Hg⁰, a volatile form that can be released from the cell.
Correct answer is: merA (mercuric reductase)
Q.16 A DNA microarray used for detecting multiple pollutants works by:
Amplifying DNA with PCR
Hybridizing labeled environmental DNA to immobilized probe sequences
Sequencing the entire genome
Measuring electrical conductivity
Explanation - Microarrays contain thousands of DNA probes; labeled DNA from the sample hybridizes to complementary probes, indicating presence of target genes.
Correct answer is: Hybridizing labeled environmental DNA to immobilized probe sequences
Q.17 What is the purpose of a promoter in a recombinant plasmid used for bioremediation?
To replicate the plasmid
To initiate transcription of the inserted gene
To degrade the plasmid after use
To provide antibiotic resistance
Explanation - Promoters are DNA sequences recognized by RNA polymerase that start transcription, controlling the expression level of the bioremediation gene.
Correct answer is: To initiate transcription of the inserted gene
Q.18 Which technique would you use to confirm that a gene has been successfully inserted into a bacterial chromosome?
Southern blot
Northern blot
Western blot
ELISA
Explanation - Southern blotting detects specific DNA sequences in genomic DNA, confirming integration of the target gene.
Correct answer is: Southern blot
Q.19 In the context of environmental DNA (eDNA) monitoring, the term ‘amplicon sequencing’ refers to:
Sequencing whole genomes of all organisms present
Sequencing a specific amplified DNA region (e.g., 16S rRNA) to profile community composition
Measuring RNA expression levels
Analyzing protein structures
Explanation - Amplicon sequencing targets conserved gene regions to identify taxa present in an environmental sample without full metagenome sequencing.
Correct answer is: Sequencing a specific amplified DNA region (e.g., 16S rRNA) to profile community composition
Q.20 Which of the following best describes a ‘synthetic biology chassis’ in environmental applications?
A vehicle for transporting microbes
A well‑characterized host organism used as a platform for genetic engineering
A type of soil
A chemical reactor
Explanation - A chassis is a standardized microbial strain (e.g., E. coli, Pseudomonas putida) engineered to carry synthetic pathways for tasks like pollutant degradation.
Correct answer is: A well‑characterized host organism used as a platform for genetic engineering
Q.21 What is the role of a riboswitch in engineered microbes for environmental monitoring?
It acts as a light source
It controls gene expression in response to a specific small molecule
It transports electrons
It degrades DNA
Explanation - Riboswitches are RNA elements that alter transcription or translation when bound by a ligand, enabling conditional expression of reporter or remediation genes.
Correct answer is: It controls gene expression in response to a specific small molecule
Q.22 Which of the following is a common method for delivering plasmids into environmental bacteria?
Electroporation
Centrifugation
Spectrophotometry
Chromatography
Explanation - Electroporation uses a brief electric pulse to create pores in the cell membrane, allowing plasmid DNA to enter the cell.
Correct answer is: Electroporation
Q.23 A gene circuit that produces a fluorescent signal only when both nitrate and heavy metal ions are present is an example of:
A simple promoter
A logical AND gate
A feedback inhibitor
A constitutive expression system
Explanation - Synthetic gene circuits can be designed to behave like logical operators; an AND gate requires two inputs before the output (fluorescence) is activated.
Correct answer is: A logical AND gate
Q.24 Which analytical method would you pair with metagenomic sequencing to quantify the activity of pollutant‑degrading genes?
qRT‑PCR
Chromatography
Mass spectrometry
Flow cytometry
Explanation - Quantitative reverse transcription PCR measures transcript levels of target genes, providing insight into their expression and activity in situ.
Correct answer is: qRT‑PCR
Q.25 In a bioelectrochemical system, engineered microbes convert pollutants into electricity. The genetic element that enables electron transfer to an electrode is usually:
Cytochrome c genes
Ribosomal RNA genes
Photosystem II genes
Heat‑shock protein genes
Explanation - Cytochromes act as electron carriers; overexpressing outer‑membrane cytochromes (e.g., mtrC) enhances extracellular electron transfer to electrodes.
Correct answer is: Cytochrome c genes
Q.26 Which of the following best describes ‘horizontal gene transfer’ (HGT) in the context of environmental biotech?
Transfer of genes from parent to offspring
Transfer of genetic material between unrelated organisms, often via plasmids or transposons
Transfer of genes from mitochondria to nucleus
Transfer of genes through viral infection only
Explanation - HGT allows microbes to acquire new catabolic pathways from other species, facilitating natural bioremediation processes.
Correct answer is: Transfer of genetic material between unrelated organisms, often via plasmids or transposons
Q.27 Which of these is a limitation of using CRISPR‑Cas systems in open‑environment applications?
High cost of reagents
Potential off‑target effects and horizontal spread of edited genes
Inability to edit DNA
Requirement for high temperature
Explanation - In environmental releases, unintended edits or gene flow to native microbes raise ecological and regulatory concerns.
Correct answer is: Potential off‑target effects and horizontal spread of edited genes
Q.28 A synthetic operon designed to degrade phenol includes a promoter, a transcriptional regulator, and the catA gene. The regulator’s role is to:
Transport phenol into the cell
Bind phenol and activate the promoter when phenol is present
Break down phenol directly
Provide resistance to antibiotics
Explanation - Regulatory proteins can sense specific substrates (phenol) and induce transcription of downstream catabolic genes.
Correct answer is: Bind phenol and activate the promoter when phenol is present
Q.29 What is the primary purpose of using a terminator sequence in a recombinant construct?
To stop transcription downstream of the gene of interest
To start DNA replication
To enhance translation efficiency
To confer antibiotic resistance
Explanation - Terminators signal RNA polymerase to end transcription, preventing read‑through into neighboring genes.
Correct answer is: To stop transcription downstream of the gene of interest
Q.30 Which of the following best describes ‘bioprecipitation’ in engineered microbes?
Formation of insoluble metal sulfides inside the cell to immobilize heavy metals
Release of gases from the cell
Synthesis of vitamins
Conversion of sugars to ethanol
Explanation - Engineered microbes can express sulfide‑producing enzymes that precipitate metals as insoluble compounds, aiding remediation.
Correct answer is: Formation of insoluble metal sulfides inside the cell to immobilize heavy metals
Q.31 In the context of gene editing for pollutant degradation, a ‘knock‑in’ strategy refers to:
Removing a gene from the genome
Introducing a new gene at a specific locus
Increasing the copy number of a plasmid
Silencing gene expression with RNAi
Explanation - Knock‑in inserts a functional gene into a defined genomic position, ensuring stable expression.
Correct answer is: Introducing a new gene at a specific locus
Q.32 Which of the following is an advantage of using a fluorescent reporter (e.g., GFP) over a colorimetric reporter (e.g., lacZ) in environmental monitoring?
Fluorescence can be detected in real time without substrate addition
Fluorescence is visible to the naked eye
GFP is cheaper than lacZ
GFP works only in anaerobic conditions
Explanation - GFP emits light upon excitation, allowing non‑invasive, continuous monitoring of gene expression in living cells.
Correct answer is: Fluorescence can be detected in real time without substrate addition
Q.33 When constructing a library of environmental DNA fragments for functional screening, which host is most commonly used?
Saccharomyces cerevisiae
Escherichia coli
Arabidopsis thaliana
Drosophila melanogaster
Explanation - E. coli is a fast‑growing, well‑characterized bacterium that efficiently expresses heterologous DNA for functional assays.
Correct answer is: Escherichia coli
Q.34 A ‘synthetic promoter’ engineered to respond to arsenic ions is most likely based on:
A random DNA sequence
An arsenic‑responsive regulatory element fused to a core promoter
A viral promoter
A ribosomal RNA promoter
Explanation - Synthetic promoters combine a sensing element (e.g., ArsR binding site) with a minimal promoter to drive conditional transcription.
Correct answer is: An arsenic‑responsive regulatory element fused to a core promoter
Q.35 Which of the following is a standard method for measuring the degradation rate of a pollutant by engineered microbes?
Measuring optical density at 600 nm
Quantifying residual pollutant concentration over time using chromatography
Counting colony forming units
Measuring ATP levels
Explanation - Techniques such as HPLC or GC‑MS track the decrease in pollutant concentration, providing kinetic data on biodegradation.
Correct answer is: Quantifying residual pollutant concentration over time using chromatography
Q.36 In a CRISPR‑based gene drive designed to spread a degradative pathway through a wild population, the key component ensuring inheritance bias is:
Cas9 nuclease
Guide RNA only
A selectable antibiotic marker
A fluorescent protein
Explanation - Cas9 cuts the wild‑type allele; the cell repairs the break using the drive cassette as a template, copying the engineered trait into the homologous chromosome.
Correct answer is: Cas9 nuclease
Q.37 Which of the following is a major ethical concern regarding the release of genetically engineered microbes for bioremediation?
High cost of production
Potential disruption of native microbial ecosystems
Inability to degrade any pollutant
Difficulty in measuring pH
Explanation - Engineered strains could outcompete or transfer genes to native microbes, altering community dynamics and ecological balance.
Correct answer is: Potential disruption of native microbial ecosystems
Q.38 A plasmid designed for environmental release often contains a ‘kill switch’. Its purpose is to:
Enhance gene expression
Induce cell death under specific conditions to prevent uncontrolled spread
Increase plasmid copy number
Provide resistance to heavy metals
Explanation - Kill switches are genetic circuits that trigger cell death (e.g., via toxin expression) when a predefined environmental cue is absent.
Correct answer is: Induce cell death under specific conditions to prevent uncontrolled spread
Q.39 Which of the following sequencing approaches is most suitable for detecting low‑abundance antibiotic‑resistance genes in a contaminated soil sample?
Shotgun metagenomics with deep sequencing depth
Sanger sequencing of a single isolate
RNA‑seq of plant roots
DNA fingerprinting
Explanation - Deep shotgun sequencing provides enough coverage to capture rare genetic elements within a complex community.
Correct answer is: Shotgun metagenomics with deep sequencing depth
Q.40 The term ‘biocontainment’ in the context of engineered environmental microbes primarily refers to:
Physical barriers like tanks
Genetic strategies that limit survival outside intended sites
Using high‑pressure reactors
Increasing temperature tolerance
Explanation - Biocontainment involves designing genetic safeguards (auxotrophies, kill switches) that restrict the organism’s viability to specific environments.
Correct answer is: Genetic strategies that limit survival outside intended sites
Q.41 In the construction of a synthetic operon for chlorinated solvent degradation, the order of genes is often arranged to:
Match the natural pathway flux for optimal intermediate processing
Randomly place genes
Place the strongest promoter last
Separate genes onto different plasmids
Explanation - Placing genes in the order of metabolic steps minimizes accumulation of toxic intermediates and improves overall degradation efficiency.
Correct answer is: Match the natural pathway flux for optimal intermediate processing
Q.42 Which of the following is a key advantage of using a ‘cell‑free transcription‑translation system’ for testing environmental biosensors?
It eliminates the need for living cells, reducing biosafety concerns
It requires expensive growth media
It only works at high temperatures
It cannot produce fluorescent signals
Explanation - Cell‑free systems allow rapid prototyping of genetic circuits without live microorganisms, facilitating safe testing of biosensor designs.
Correct answer is: It eliminates the need for living cells, reducing biosafety concerns
Q.43 A gene that encodes for a heavy‑metal binding peptide (e.g., phytochelatin) is introduced into a plant for phytoremediation. This strategy exemplifies:
Horizontal gene transfer
Transgenic approach
Classical breeding
Mutation breeding
Explanation - Introducing a foreign gene into a plant genome to confer new traits is a classic transgenic method used in phytoremediation.
Correct answer is: Transgenic approach
Q.44 Which of the following is NOT a typical component of a CRISPR‑Cas12a (Cpf1) system used for gene editing?
crRNA (CRISPR RNA)
tracrRNA (trans‑activating crRNA)
Cas12a nuclease
PAM‑dependent DNA cleavage
Explanation - Cas12a requires only a crRNA; unlike Cas9, it does not need a separate tracrRNA for processing.
Correct answer is: tracrRNA (trans‑activating crRNA)
Q.45 When constructing a plasmid for environmental use, why is a ‘low‑copy‑number origin of replication’ sometimes preferred?
To reduce metabolic burden on the host and improve stability
To increase the number of plasmids per cell
To speed up DNA replication
To make the plasmid fluorescent
Explanation - Low copy numbers limit the strain on the host’s resources, enhancing plasmid maintenance over long periods in the environment.
Correct answer is: To reduce metabolic burden on the host and improve stability
Q.46 Which method is commonly used to quantify the concentration of a fluorescent reporter protein in a mixed environmental sample?
Spectrophotometry at 600 nm
Fluorometry with specific excitation/emission wavelengths
PCR amplification
Mass spectrometry
Explanation - Fluorometers detect emitted light at characteristic wavelengths, enabling sensitive quantification of fluorescent proteins like GFP.
Correct answer is: Fluorometry with specific excitation/emission wavelengths
Q.47 In the context of bioinformatics pipelines for environmental metagenomics, the term ‘assembly’ refers to:
Aligning short reads to a reference genome
Joining overlapping reads to reconstruct longer contiguous sequences (contigs)
Measuring gene expression levels
Visualizing phylogenetic trees
Explanation - Assembly builds longer DNA sequences from short sequencing reads, facilitating downstream functional annotation.
Correct answer is: Joining overlapping reads to reconstruct longer contiguous sequences (contigs)
Q.48 A synthetic gene circuit includes a negative feedback loop where the product represses its own promoter. This design typically results in:
Uncontrolled over‑expression
Stabilized expression levels and reduced noise
Complete shutdown of the pathway
Increased mutation rate
Explanation - Negative feedback dampens fluctuations, yielding more consistent protein output, which is valuable for precise bioremediation functions.
Correct answer is: Stabilized expression levels and reduced noise
Q.49 Which of the following is an example of a ‘gene cassette’ used in environmental biotechnology?
A series of linked genes flanked by recombination sites, such as an integron cassette
A single gene with its own promoter
A plasmid backbone without any insert
A ribosomal RNA operon
Explanation - Gene cassettes can be captured and expressed by integrons, allowing rapid acquisition of new functions like antibiotic resistance or pollutant degradation.
Correct answer is: A series of linked genes flanked by recombination sites, such as an integron cassette
Q.50 The use of a ‘synthetic ribosome binding site (RBS)’ in a construct primarily affects:
DNA replication speed
Translation initiation efficiency
Transcription termination
Plasmid stability
Explanation - RBS sequences determine how well ribosomes bind to mRNA, influencing protein production levels.
Correct answer is: Translation initiation efficiency
Q.51 In a bioreactor treating wastewater with engineered microbes, the measurement of dissolved oxygen (DO) is critical because:
Low DO can limit aerobic degradation pathways
DO determines the pH of the system
High DO destroys plasmids
DO controls temperature
Explanation - Many pollutant‑degrading enzymes require oxygen; insufficient DO hampers their activity, reducing treatment efficiency.
Correct answer is: Low DO can limit aerobic degradation pathways
Q.52 Which of the following best describes the function of a ‘lux operon’ when used as a reporter in environmental microbes?
It provides antibiotic resistance
It produces bioluminescence that can be detected without external illumination
It degrades heavy metals
It enhances cell motility
Explanation - The lux operon encodes enzymes that generate light, allowing real‑time, non‑invasive monitoring of gene expression.
Correct answer is: It produces bioluminescence that can be detected without external illumination
Q.53 When assessing the ecological impact of a released engineered microbe, which of the following metrics is most informative?
Growth rate in laboratory media
Horizontal gene transfer frequency to native microbes
Color of the colony on agar
Resistance to UV light
Explanation - Evaluating how readily the engineered genes spread to indigenous populations helps gauge ecological risk.
Correct answer is: Horizontal gene transfer frequency to native microbes
Q.54 A key challenge in using plasmid‑based expression systems for field applications is:
Plasmid loss in the absence of selective pressure
Excessive fluorescence
Too rapid gene expression
Inability to replicate in any host
Explanation - Without antibiotics or other selection, plasmids can be cured from the host, reducing the engineered function over time.
Correct answer is: Plasmid loss in the absence of selective pressure
Q.55 Which molecular tool can be used to silence a specific gene in a bacterial population to study its role in pollutant degradation?
CRISPR interference (CRISPRi)
RNA polymerase
DNA ligase
Taq polymerase
Explanation - CRISPRi uses a catalytically dead Cas protein (dCas) guided by sgRNA to block transcription of target genes.
Correct answer is: CRISPR interference (CRISPRi)
Q.56 In the design of a synthetic pathway for plastic (PET) degradation, the enzyme PETase is often combined with which accessory enzyme to increase efficiency?
MHETase
Lipase
Amylase
DNA polymerase
Explanation - PETase hydrolyzes PET into MHET; MHETase further degrades MHET into its monomers, completing the breakdown.
Correct answer is: MHETase
Q.57 The term ‘omics’ (e.g., genomics, proteomics) in environmental biotechnology generally refers to:
Studying single genes in isolation
Comprehensive, high‑throughput analysis of entire classes of molecules
Measuring soil temperature
Counting microbial colonies
Explanation - ‘Omics’ technologies enable global profiling of DNA, RNA, proteins, metabolites, providing system‑level insights.
Correct answer is: Comprehensive, high‑throughput analysis of entire classes of molecules
Q.58 Which of the following best describes a ‘phage‑display library’ used for environmental protein discovery?
A collection of bacteriophages each displaying a different peptide on their surface
A library of plasmids without any insert
A set of viral genomes that infect plants
A database of DNA sequences
Explanation - Phage‑display libraries present diverse peptides/proteins, allowing selection of binders to specific contaminants.
Correct answer is: A collection of bacteriophages each displaying a different peptide on their surface
Q.59 In a bioremediation field trial, which of the following would be the most direct evidence that the engineered gene is functional in situ?
Detection of the transgene DNA in soil samples
Observation of decreased pollutant concentration accompanied by expression of a reporter gene
Increase in plant height
Higher soil temperature
Explanation - Combining chemical analysis (pollutant reduction) with reporter expression confirms both activity and gene function in the environment.
Correct answer is: Observation of decreased pollutant concentration accompanied by expression of a reporter gene
Q.60 The main purpose of using a ‘terminator’ such as T7 terminator downstream of a gene cassette is to:
Increase transcription rates
Prevent transcriptional read‑through into downstream sequences
Add antibiotic resistance
Enhance plasmid replication
Explanation - Terminators signal RNA polymerase to stop transcription, ensuring discrete transcription units and reducing unintended expression.
Correct answer is: Prevent transcriptional read‑through into downstream sequences
Q.61 A synthetic biology platform that uses ‘modular cloning (MoClo)’ relies on:
Type IIS restriction enzymes that enable scar‑less assembly of multiple DNA parts
Random ligation of DNA fragments
CRISPR editing of plasmids in vivo
Electroporation of whole genomes
Explanation - MoClo utilizes enzymes like BsaI to generate compatible overhangs, allowing hierarchical, standardized assembly of genetic modules.
Correct answer is: Type IIS restriction enzymes that enable scar‑less assembly of multiple DNA parts
Q.62 In the context of engineered microbial consortia for pollutant degradation, ‘division of labor’ refers to:
All cells performing the same function simultaneously
Different strains each carrying a subset of the metabolic pathway
Using only one species for the whole process
Applying chemicals to boost activity
Explanation - Division of labor distributes metabolic steps among specialized members, improving overall efficiency and stability.
Correct answer is: Different strains each carrying a subset of the metabolic pathway
Q.63 Which of the following is a commonly used selective medium for isolating bacteria that can degrade phenol?
Minimal salts medium with phenol as the sole carbon source
Luria‑Bertani agar with glucose
MacConkey agar with lactose
Blood agar
Explanation - Only phenol‑utilizing bacteria can grow when phenol is the sole carbon and energy source, allowing selection.
Correct answer is: Minimal salts medium with phenol as the sole carbon source
Q.64 A genetic construct includes a riboswitch that responds to arsenic and controls expression of a reporter gene. When arsenic is present, the reporter is:
Repressed
Activated
Unchanged
Degraded
Explanation - Arsenic‑binding riboswitches typically undergo conformational change that permits translation of the downstream gene upon ligand binding.
Correct answer is: Activated
Q.65 Which of the following is a major advantage of using ‘synthetic minimal cells’ for environmental biosensing?
They can replicate indefinitely
They lack unwanted metabolic background, reducing false signals
They require complex growth media
They are larger than natural cells
Explanation - Minimal cells contain only essential components, providing a clean chassis for precise sensing without interference from native pathways.
Correct answer is: They lack unwanted metabolic background, reducing false signals
Q.66 The enzyme dehalogenase used for chlorinated solvent bioremediation belongs to which enzyme class?
Oxidoreductases
Hydrolases
Transferases
Ligases
Explanation - Dehalogenases catalyze the hydrolytic removal of halogen atoms from organic compounds.
Correct answer is: Hydrolases
Q.67 When designing a genetic circuit that must function under fluctuating temperature conditions in a river, which regulatory element is most suitable?
A temperature‑sensitive promoter
A constitutive strong promoter
A light‑responsive riboswitch
An antibiotic‑inducible promoter
Explanation - Temperature‑responsive promoters modulate gene expression according to ambient temperature, ensuring appropriate activity in variable environments.
Correct answer is: A temperature‑sensitive promoter
Q.68 Which of the following bioinformatics tools is specifically designed for annotating functional genes involved in biodegradation pathways?
KEGG Mapper
BLAST
PROKKA with the Biocyc database
MetaCyc
Explanation - MetaCyc contains curated metabolic pathways, including those for xenobiotic degradation, facilitating functional annotation of environmental genes.
Correct answer is: MetaCyc
Q.69 In a field deployment, engineered microbes are often encapsulated in a hydrogel matrix. The primary purpose of this encapsulation is to:
Increase gene expression levels
Provide physical containment and protect cells from shear stress
Make the microbes fluorescent
Accelerate plasmid replication
Explanation - Hydrogel matrices immobilize cells, limit dispersal, and shield them from harsh environmental forces while allowing substrate diffusion.
Correct answer is: Provide physical containment and protect cells from shear stress
Q.70 Which of the following is a potential drawback of using a strong constitutive promoter in an engineered microbe for pollutant degradation?
Reduced metabolic burden
Uncontrolled expression leading to growth inhibition
Improved plasmid stability
Enhanced environmental safety
Explanation - Overexpression of metabolic enzymes can impose a high energetic cost, reducing host fitness and survivability.
Correct answer is: Uncontrolled expression leading to growth inhibition
Q.71 The term ‘bioreactor’ in the context of environmental biotechnology most accurately describes:
A device that measures pH
A controlled vessel where microorganisms degrade contaminants under optimized conditions
A type of solar panel
A computer simulation model
Explanation - Bioreactors provide controlled environments (temperature, aeration, mixing) for efficient microbial biotransformation of waste streams.
Correct answer is: A controlled vessel where microorganisms degrade contaminants under optimized conditions
Q.72 A DNA barcode used for species identification in environmental samples typically targets which genetic region?
16S rRNA gene for bacteria and ITS region for fungi
Cytochrome c oxidase I (COI) for animals only
Chloroplast rbcL for plants only
Mitochondrial D-loop for all organisms
Explanation - The 16S rRNA gene (bacteria) and ITS region (fungi) are standard barcodes for taxonomic identification in metagenomics.
Correct answer is: 16S rRNA gene for bacteria and ITS region for fungi
Q.73 Which of the following genetic parts is essential for ensuring that a gene is transcribed in a prokaryotic system?
Promoter
Poly‑A tail
Spliceosome
Karyotype
Explanation - Promoters contain consensus sequences recognized by RNA polymerase to initiate transcription in prokaryotes.
Correct answer is: Promoter
Q.74 In the context of environmental biotechnology, the term ‘biodegradability index’ usually refers to:
A metric comparing the rate of microbial degradation to a reference substrate
The electrical conductivity of soil
The color intensity of a dye
The pH of a solution
Explanation - The biodegradability index quantifies how readily a compound is broken down relative to a standard, guiding remediation strategies.
Correct answer is: A metric comparing the rate of microbial degradation to a reference substrate
Q.75 Which of the following best explains why a gene encoding a membrane-bound monooxygenase might be fused to a solubility‑enhancing tag in an engineered microbe?
To improve protein folding and increase functional expression
To make the cell more rigid
To reduce the gene size
To change the enzyme’s substrate specificity
Explanation - Solubility tags (e.g., MBP, GST) aid proper folding of membrane proteins, enhancing activity in heterologous hosts.
Correct answer is: To improve protein folding and increase functional expression
Q.76 Which analytical technique is most commonly used to confirm the presence of a specific plasmid-borne gene in an engineered bacterial isolate?
PCR with gene‑specific primers
Gel filtration chromatography
Mass spectrometry of lipids
Flow cytometry
Explanation - PCR amplifies the target gene region, providing a rapid and specific check for its presence.
Correct answer is: PCR with gene‑specific primers
Q.77 A key feature of ‘synthetic gene clusters’ used for biosynthetic pathway engineering is:
Random gene order
Co‑localization of all pathway genes on a single construct to ensure coordinated expression
Inclusion of eukaryotic introns
Absence of promoters
Explanation - Clustering genes simplifies regulation, facilitates transfer between hosts, and improves metabolic flux.
Correct answer is: Co‑localization of all pathway genes on a single construct to ensure coordinated expression
Q.78 Which of the following is a typical safety measure for preventing the spread of antibiotic‑resistance markers from engineered microbes into the environment?
Using antibiotic‑free selection systems such as auxotrophic complementation
Increasing the antibiotic concentration
Adding more plasmid copies
Overexpressing resistance genes
Explanation - Auxotrophic markers require the host to synthesize an essential metabolite, avoiding the release of antibiotic resistance genes.
Correct answer is: Using antibiotic‑free selection systems such as auxotrophic complementation
Q.79 When performing a quantitative comparison of two engineered strains for benzene degradation, which statistical test is most appropriate for evaluating differences in degradation rates?
Chi‑square test
Student’s t‑test (unpaired)
Mann‑Whitney U test
ANOVA with post‑hoc Tukey
Explanation - When comparing the means of two independent groups with normally distributed data, an unpaired t‑test is appropriate.
Correct answer is: Student’s t‑test (unpaired)
Q.80 In a synthetic biology framework, a ‘chassis’ organism that is naturally resistant to heavy metals is advantageous because:
It eliminates the need for genetic engineering
It can survive in contaminated sites while expressing remediation genes
It grows faster than all other microbes
It produces fluorescent pigments
Explanation - Intrinsic resistance allows the chassis to tolerate toxic conditions, providing a stable platform for engineered functions.
Correct answer is: It can survive in contaminated sites while expressing remediation genes
Q.81 Which of the following statements about CRISPR base editors is true in the context of environmental biotechnology?
They create double‑strand breaks to insert large genes
They enable precise nucleotide changes without double‑strand breaks, useful for fine‑tuning enzyme activity
They are only functional in eukaryotes
They cannot be delivered via plasmids
Explanation - Base editors fuse a deaminase to a dead Cas protein, allowing targeted point mutations, ideal for optimizing enzyme specificity without inducing DSBs.
Correct answer is: They enable precise nucleotide changes without double‑strand breaks, useful for fine‑tuning enzyme activity
Q.82 A biosensor designed to detect atrazine in water uses a transcription factor that binds atrazine and activates expression of a reporter. This system exemplifies:
Post‑translational regulation
Transcriptional activation by a ligand‑responsive regulator
RNA interference
Protein degradation pathway
Explanation - The atrazine‑binding transcription factor acts as a sensor, turning on reporter gene transcription only when the pollutant is present.
Correct answer is: Transcriptional activation by a ligand‑responsive regulator
Q.83 Which of the following best describes the purpose of using a ‘dual‑promoter system’ in an engineered microbe for simultaneous expression of a catabolic enzyme and a reporter?
To ensure both genes are transcribed at comparable levels from separate promoters
To fuse the two genes into a single protein
To inhibit expression of the reporter
To degrade the plasmid after use
Explanation - Dual promoters allow independent, balanced expression of multiple genes, facilitating both function and monitoring.
Correct answer is: To ensure both genes are transcribed at comparable levels from separate promoters
Q.84 In the context of field‑scale bioremediation, the term ‘in situ’ means:
Treating the contaminated material directly at the site without excavation
Removing soil for treatment in a laboratory
Using only chemical reagents
Applying heat to the site
Explanation - In‑situ remediation addresses contaminants where they reside, minimizing disturbance and transport costs.
Correct answer is: Treating the contaminated material directly at the site without excavation
Q.85 A synthetic transcription factor that activates gene expression only under low‑oxygen conditions is most suitable for engineering microbes that will operate in:
Aerobic surface waters
Anaerobic sediments
High‑light environments
Sterile laboratory media
Explanation - Oxygen‑responsive regulators enable expression of degradation pathways only where the target environment lacks oxygen.
Correct answer is: Anaerobic sediments
Q.86 Which of the following is an example of a ‘bioelectrochemical system’ that couples microbial metabolism with electricity generation for pollutant removal?
Microbial fuel cell (MFC)
Photobioreactor
Aerobic composting bin
Biogas digester
Explanation - MFCs harness electrons transferred from microbes degrading organic pollutants to an anode, producing electricity while treating waste.
Correct answer is: Microbial fuel cell (MFC)
Q.87 When constructing a plasmid for use in a Gram‑positive bacterium, which origin of replication is most appropriate?
pUC (E. coli origin)
pBR322
pAMβ1
pUC19
Explanation - pAMβ1 is a broad‑host‑range origin that functions in many Gram‑positive species, unlike pUC which is specific to E. coli.
Correct answer is: pAMβ1
Q.88 In a metagenomic library screening for oil‑degrading enzymes, the most efficient initial screen is often based on:
Colorimetric detection of cleared oil droplets on agar plates
Measuring cell density in liquid culture
Sequencing all clones
Electron microscopy
Explanation - Colonies that produce halos indicate enzymatic breakdown of oil substrates, allowing rapid identification of positive clones.
Correct answer is: Colorimetric detection of cleared oil droplets on agar plates
Q.89 Which of the following molecular tools can be used to integrate a gene directly into the chromosome of a bacterial host, avoiding plasmid maintenance?
Suicide vector with homologous recombination
High‑copy‑number plasmid
RNA polymerase
Restriction enzyme only
Explanation - Suicide vectors cannot replicate in the host; they integrate via homologous recombination, resulting in stable chromosomal insertion.
Correct answer is: Suicide vector with homologous recombination
Q.90 A gene circuit that produces a fluorescent signal only after exposure to both nitrate and copper ions demonstrates which logical operation?
OR gate
AND gate
NOT gate
XOR gate
Explanation - Both inputs must be present simultaneously for the output (fluorescence) to be activated, characteristic of an AND gate.
Correct answer is: AND gate
Q.91 When using a qPCR assay to quantify the abundance of a mercury‑resistance gene (merA) in a soil sample, which reference is essential for accurate normalization?
Total DNA concentration
16S rRNA gene copy number
Soil moisture content
Ambient temperature
Explanation - Normalizing to a universal marker like 16S rRNA accounts for variations in microbial biomass across samples.
Correct answer is: 16S rRNA gene copy number
Q.92 Which of the following best explains why a gene encoding a metal‑binding peptide is often fused to a secretion signal when expressed in Gram‑negative bacteria for bioremediation?
To ensure the peptide is exported outside the cell where metal ions are present
To increase intracellular metal accumulation
To make the peptide fluorescent
To degrade the peptide after synthesis
Explanation - Secretion signals direct the peptide to the periplasm or extracellular space, allowing it to bind and sequester metals from the environment.
Correct answer is: To ensure the peptide is exported outside the cell where metal ions are present
Q.93 A synthetic pathway for degrading a chlorinated aromatic compound requires three enzymes in a specific order. Which design principle ensures optimal flux through the pathway?
Co‑localization of enzymes using scaffold proteins
Random insertion of genes
Using separate plasmids for each enzyme
Expressing only the first enzyme
Explanation - Scaffolds bring enzymes into close proximity, minimizing diffusion of intermediates and enhancing overall pathway efficiency.
Correct answer is: Co‑localization of enzymes using scaffold proteins
Q.94 Which of the following is a common method for measuring the activity of a dioxygenase enzyme engineered for aromatic compound degradation?
Monitoring the decrease in substrate absorbance at a specific wavelength
Counting colony forming units
Measuring ATP levels
Assessing cell morphology under a microscope
Explanation - Many aromatic substrates have characteristic absorbance peaks; their disappearance over time indicates enzymatic conversion.
Correct answer is: Monitoring the decrease in substrate absorbance at a specific wavelength
Q.95 In a CRISPR‑Cas9 gene‑drive system intended for spreading a pollutant‑degrading trait, the guide RNA is designed to target:
A neutral genomic site to avoid off‑target effects
The wild‑type allele of the target gene
A plasmid backbone sequence
A mitochondrial gene
Explanation - The guide RNA directs Cas9 to cut the wild‑type allele, prompting the cell to repair using the drive allele as a template, thus copying the trait.
Correct answer is: The wild‑type allele of the target gene
Q.96 Which of the following best describes the function of an ‘auxotrophic marker’ in a plasmid used for environmental applications?
Provides resistance to antibiotics
Complements a metabolic deficiency, allowing growth only if the plasmid is present
Encodes a fluorescent protein
Increases plasmid copy number
Explanation - Auxotrophic markers restore a missing nutrient synthesis pathway, ensuring plasmid maintenance without antibiotics.
Correct answer is: Complements a metabolic deficiency, allowing growth only if the plasmid is present
Q.97 When designing a synthetic riboswitch that responds to a pollutant, which part of the riboswitch directly interacts with the ligand?
Aptamer domain
Promoter region
Ribosome binding site
Terminator sequence
Explanation - The aptamer domain folds into a three‑dimensional structure that selectively binds the target molecule, triggering conformational changes.
Correct answer is: Aptamer domain
Q.98 A researcher wants to assess the potential horizontal transfer of a degradation plasmid from engineered bacteria to native soil microbes. Which technique would provide the most direct evidence?
Conjugation assay followed by selective plating of native isolates
Measuring soil pH before and after inoculation
Counting total microbial cells with a hemocytometer
Analyzing soil texture
Explanation - Conjugation assays detect plasmid transfer events by selecting for the plasmid marker in previously plasmid‑free native strains.
Correct answer is: Conjugation assay followed by selective plating of native isolates
Q.99 Which of the following is an advantage of using a cell‑free expression system for rapid prototyping of a biosensor circuit?
Eliminates the need for DNA purification
Allows testing without living cells, reducing biosafety concerns
Provides unlimited protein production
Requires high‑temperature incubation
Explanation - Cell‑free systems contain the transcription‑translation machinery in vitro, enabling quick testing of genetic designs without live organisms.
Correct answer is: Allows testing without living cells, reducing biosafety concerns
Q.100 In the context of environmental DNA (eDNA) monitoring, why is the 12S rRNA gene commonly targeted for detecting vertebrate species?
It is highly conserved and provides species‑level resolution for vertebrates
It encodes a membrane protein
It is only present in bacteria
It is the largest gene in the genome
Explanation - The mitochondrial 12S rRNA gene contains variable regions suitable for distinguishing vertebrate species in eDNA studies.
Correct answer is: It is highly conserved and provides species‑level resolution for vertebrates
Q.101 A synthetic operon for degrading naphthalene includes the genes nahA, nahB, and nahC. If nahB encodes a rate‑limiting enzyme, which engineering strategy would most likely improve overall degradation?
Increase the ribosome binding site strength upstream of nahB
Delete the nahB gene
Place nahB on a separate low‑copy plasmid
Introduce a terminator after nahA
Explanation - Strengthening the RBS enhances translation of the rate‑limiting enzyme, increasing its cellular concentration and pathway flux.
Correct answer is: Increase the ribosome binding site strength upstream of nahB
Q.102 Which of the following best explains why a ‘kill switch’ based on toxin‑antitoxin system is preferable over a simple toxin gene for biocontainment?
The antitoxin can neutralize the toxin under permissive conditions, preventing accidental cell death
It is cheaper to synthesize
It works only in eukaryotes
It increases plasmid copy number
Explanation - Toxin‑antitoxin systems allow conditional activation: the antitoxin is expressed under normal conditions, while the toxin is expressed only under defined triggers.
Correct answer is: The antitoxin can neutralize the toxin under permissive conditions, preventing accidental cell death
Q.103 When measuring the expression level of a fluorescent reporter gene in a mixed environmental sample using flow cytometry, the primary data obtained are:
Fluorescence intensity per individual cell
Total DNA concentration
pH of the sample
Temperature of the chamber
Explanation - Flow cytometry quantifies fluorescence on a per‑cell basis, allowing assessment of reporter expression across heterogeneous populations.
Correct answer is: Fluorescence intensity per individual cell
Q.104 A bioremediation strategy aims to use engineered algae to capture excess nitrate from agricultural runoff. Which genetic modification would most directly enhance nitrate uptake?
Overexpression of nitrate transporter genes (e.g., NRT1)
Insertion of a fluorescent protein gene
Knock‑out of photosystem II genes
Insertion of an antibiotic resistance gene
Explanation - Increasing the number of nitrate transporters improves the organism’s capacity to import and assimilate nitrate from the environment.
Correct answer is: Overexpression of nitrate transporter genes (e.g., NRT1)
Q.105 Which of the following best defines ‘synthetic auxotrophy’ used as a biocontainment strategy?
Engineering a strain that requires an unnatural nutrient not found in nature to survive
Making the strain resistant to all antibiotics
Deleting all metabolic pathways
Adding extra copies of essential genes
Explanation - Synthetic auxotrophy creates a dependency on a synthetic compound, preventing survival outside controlled environments where the compound is supplied.
Correct answer is: Engineering a strain that requires an unnatural nutrient not found in nature to survive
Q.106 In a synthetic gene circuit, a ‘feed‑forward loop’ where an activator also activates a repressor that later inhibits the activator results in:
Immediate and sustained expression
A pulse of expression followed by attenuation
No expression at all
Random expression spikes
Explanation - Coherent feed‑forward loops can generate a transient response, where the activator initiates transcription, but the delayed repressor shuts it down, creating a pulse.
Correct answer is: A pulse of expression followed by attenuation
Q.107 Which of the following is a typical reason for using a low‑induction temperature (e.g., 16 °C) during expression of a heterologous enzyme in E. coli?
To increase the rate of protein synthesis
To improve protein folding and solubility
To accelerate plasmid replication
To induce antibiotic resistance
Explanation - Lower temperatures slow translation, allowing nascent polypeptides to fold correctly and reducing inclusion body formation.
Correct answer is: To improve protein folding and solubility
Q.108 A researcher wishes to quantify the expression of a mercury‑responsive promoter using a fluorescent protein. Which experimental control is essential?
A strain lacking the fluorescent reporter gene
A strain with a constitutive fluorescent reporter
A strain grown in complete darkness
A strain with an unrelated antibiotic resistance gene
Explanation - A constitutive reporter provides a baseline fluorescence to normalize for cell density and instrument variation.
Correct answer is: A strain with a constitutive fluorescent reporter
Q.109 In the design of a synthetic metabolic pathway for degrading polycyclic aromatic hydrocarbons (PAHs), why is it advantageous to include a NAD(P)H regeneration module?
It reduces the need for oxygen
It supplies reducing equivalents required for many oxidative degradation steps
It increases plasmid size
It blocks gene expression
Explanation - Many PAH‑degrading enzymes are monooxygenases that require NAD(P)H; regenerating this cofactor sustains pathway activity.
Correct answer is: It supplies reducing equivalents required for many oxidative degradation steps
Q.110 Which of the following best describes the function of a ‘synthetic ribosome binding site calculator’ in genetic design?
Predicts the strength of translation initiation based on sequence context
Calculates plasmid copy number
Designs primers for PCR
Models metabolic flux
Explanation - RBS calculators estimate translation rates, enabling rational tuning of protein expression levels in synthetic constructs.
Correct answer is: Predicts the strength of translation initiation based on sequence context
Q.111 A biosensor that emits a luminescent signal in response to arsenic uses the lux operon from Vibrio fischeri. Which component of the lux operon directly catalyzes light production?
luxA
luxC
luxR
luxI
Explanation - luxA encodes the α‑subunit of the luciferase enzyme, which catalyzes the oxidation of FMNH₂ and a long‑chain aldehyde, emitting light.
Correct answer is: luxA
Q.112 In a field test, engineered microbes show rapid degradation of a target pollutant but also a decline in population after one week. Which engineering modification could improve long‑term persistence?
Introduce a synthetic auxotrophy requiring a supplemental nutrient supplied in the field
Add a constitutive antibiotic resistance marker
Increase the copy number of the plasmid
Remove all stress‑response genes
Explanation - Providing the required synthetic nutrient only at the site sustains the engineered strain while limiting spread, enhancing persistence.
Correct answer is: Introduce a synthetic auxotrophy requiring a supplemental nutrient supplied in the field
Q.113 Which of the following best illustrates the concept of ‘gene shuffling’ in directed evolution of enzymes for environmental applications?
Recombining fragments of related genes to create chimeric enzymes with improved activity
Randomly mutating a single nucleotide
Cloning the gene into a high‑copy plasmid
Expressing the gene in a eukaryotic host
Explanation - Gene shuffling mixes homologous gene segments, generating diversity that can be screened for enhanced catalytic properties.
Correct answer is: Recombining fragments of related genes to create chimeric enzymes with improved activity
Q.114 When assessing the environmental impact of a genetically engineered microbe, which of the following is a key ecological metric?
The strain’s growth rate in rich media
The change in native microbial diversity measured by 16S rRNA sequencing
The color of the colony on agar
The number of plasmid copies per cell
Explanation - Assessing shifts in community composition indicates how the engineered microbe influences ecosystem balance.
Correct answer is: The change in native microbial diversity measured by 16S rRNA sequencing
Q.115 A synthetic promoter designed for use in a marine environment must be tolerant to high salt concentrations. Which promoter characteristic would most likely be beneficial?
High GC content to improve DNA stability
Presence of salt‑responsive regulatory motifs
A strong T7 promoter
Inclusion of introns
Explanation - Regulatory elements that respond to osmotic stress enable the promoter to function effectively under high‑salinity conditions.
Correct answer is: Presence of salt‑responsive regulatory motifs