75 free MCQs on Biotechnology: Principles and Processes with worked answers and explanations. Recombinant DNA, GMOs, PCR, CRISPR, and biotechnology applications. Growing importance in NEET.
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Recombinant DNA technology: a gene of interest and plasmid are cut by the same restriction enzyme, ligated into a recombinant plasmid, and introduced into a host cell.
Q1.
The restriction enzyme EcoRI was isolated from which organism?
Answer: A. Escherichia coli
Why: The name EcoRI comes from Escherichia coli RY13, the bacterium from which this restriction endonuclease was isolated.
Q2.
In the name of a restriction enzyme like EcoRI, the first letter is derived from the:
Answer: B. Genus name
Why: In a restriction enzyme name, the first letter comes from the genus and the next two letters from the species of the prokaryote.
Q3.
Which of the following is used to make the bacterial cell wall competent to take up DNA in transformation?
Answer: C. Divalent calcium ions
Why: Treating cells with a specific concentration of a divalent cation such as calcium increases the efficiency with which DNA enters the bacterium through pores in its wall.
Q4.
Palindromic sequences that are recognised by restriction enzymes read the same:
Answer: D. In the same orientation on both strands when read 5 to 3
Why: A palindrome in DNA is a sequence of base pairs that reads the same on the two strands when the orientation of reading is kept the same (5 to 3).
Q5.
The cutting of DNA by restriction endonucleases followed by separation of fragments is visualised using:
Answer: A. Gel electrophoresis
Why: DNA fragments produced by restriction digestion are separated and visualised by agarose gel electrophoresis.
Q6.
Restriction enzymes are used to:
Answer: B. Cut DNA at specific sequences
Why: Restriction enzymes (endonucleases) cut DNA at specific recognition sequences. They are molecular scissors for genetic engineering.
Q7.
PCR (Polymerase Chain Reaction) is used to:
Answer: B. Amplify specific DNA sequences
Why: PCR amplifies (copies) a specific DNA sequence millions of times. Used in forensics, medical diagnosis, and research.
Q8.
A plasmid is:
Answer: B. Small circular extrachromosomal DNA in bacteria (used as vector)
Why: Plasmid: small circular DNA in bacteria, separate from chromosomal DNA. Used as vectors to carry foreign genes in recombinant DNA technology.
Q9.
Bt crops contain a gene from:
Answer: B. Bacillus thuringiensis bacteria (insect-resistant toxin)
Why: Bt crops contain the Cry gene from Bacillus thuringiensis, which produces a toxin against specific insect pests. E.g., Bt cotton, Bt brinjal.
Q10.
Gel electrophoresis separates DNA fragments by:
Answer: B. Size (smaller fragments travel farther)
Why: In gel electrophoresis, DNA fragments migrate through agarose gel in an electric field. Smaller fragments travel faster and farther.
Q11.
The first product produced by recombinant DNA technology for medical use was:
Answer: B. Human insulin (from E. coli)
Why: Recombinant human insulin was the first major product of biotechnology (1982). The insulin gene was inserted into E. coli.
Q12.
ELISA test is used for:
Answer: B. Detection of antibodies or antigens (e.g., HIV test)
Why: ELISA (Enzyme-Linked Immunosorbent Assay) detects specific antigens or antibodies. Used for HIV, hepatitis, pregnancy tests.
Q13.
A vector in genetic engineering is:
Answer: B. Carrier of foreign DNA into a host cell (e.g., plasmid or virus)
Why: A vector (plasmid, bacteriophage, or viral vector) carries the foreign gene into the host cell for replication and expression.
Q14.
Golden Rice is a transgenic crop that produces:
Answer: B. Vitamin A (beta-carotene) in grain
Why: Golden Rice is engineered to produce beta-carotene (Vitamin A precursor) in the grain to address Vitamin A deficiency in developing countries.
Q15.
The enzyme DNA ligase is used to:
Answer: B. Join DNA fragments together
Why: DNA ligase seals (joins) the nicks between DNA fragments, creating a continuous strand. Called molecular glue.
Q16.
CRISPR-Cas9 is a technology for:
Answer: B. Gene editing (cutting specific DNA sequences)
Why: CRISPR-Cas9 uses a guide RNA to direct the Cas9 nuclease to cut a specific DNA sequence, enabling precise gene editing.
Q17.
Hybridoma technology is used to produce:
Answer: B. Monoclonal antibodies
Why: Hybridoma technology fuses antibody-producing B cells with cancer cells (myeloma) to create immortal hybridomas that produce monoclonal antibodies.
Q18.
Sticky ends are produced when restriction enzymes make:
Answer: B. Staggered cuts leaving single-stranded overhangs
Why: Staggered cuts by restriction enzymes leave short single-stranded extensions (sticky/cohesive ends) that can pair with complementary sticky ends.
Q19.
Fermentation used in biotechnology means:
Answer: B. Microbial or enzymatic conversion of organic compounds (can produce medicines, food, etc.)
Why: Fermentation in biotechnology: microorganisms or their enzymes convert substrates to products. Used to make antibiotics, enzymes, vitamins, alcohol, and more.
Q20.
What do restriction enzymes do to DNA?
Answer: A. Cut DNA
Why: Restriction enzymes cut DNA at specific sites.
Q21.
Which enzyme joins two DNA fragments?
Answer: A. DNA ligase
Why: DNA ligase seals fragments by forming phosphodiester bonds.
Q22.
Which is a commonly used cloning vector?
Answer: A. Plasmid
Why: Plasmids are widely used cloning vectors.
Q23.
PCR is used to do what to DNA?
Answer: A. Amplify DNA
Why: PCR amplifies a target DNA segment many-fold.
Q24.
Gel electrophoresis separates DNA fragments by?
Answer: A. Size
Why: Electrophoresis separates DNA fragments by size.
Q25.
Which organism is a common host for cloning?
Answer: A. E. coli
Why: E. coli is a standard bacterial cloning host.
Q26.
During gel electrophoresis the separated DNA bands cannot be seen directly. They are visualised by staining with a dye and then exposing the gel to:
Answer: B. UV radiation
Why: DNA separated on an agarose gel is stained with ethidium bromide and exposed to UV radiation, under which the DNA bands appear as bright orange bands.
Q27.
The separated DNA bands are cut out from the gel and extracted from the gel piece in a process known as:
Answer: C. Elution
Why: The process of extracting the separated DNA fragment from the cut-out gel piece is called elution; these purified fragments are then used in cloning.
Q28.
A good cloning vector must have an origin of replication (ori). What is the role of this sequence?
Answer: D. It controls copy number and initiates replication
Why: The ori is the sequence where replication starts; any linked DNA replicates from it, and it also governs the copy number of the vector in the host.
Q29.
In the plasmid pBR322, insertion of foreign DNA into the tetracycline-resistance gene inactivates it. This loss of a trait used to detect recombinants is called:
Answer: A. Insertional inactivation
Why: When foreign DNA is inserted within a marker gene such as tetracycline resistance, the gene is inactivated; this insertional inactivation lets recombinants be selected.
Q30.
A bioreactor differs from a simple flask culture mainly because it can:
Answer: B. Process large volumes under controlled conditions
Why: A bioreactor provides optimal conditions for growth by regulating temperature, pH, oxygen and agitation, allowing large volumes (often 100-1000 litres) to be processed.
Q31.
The polymerase chain reaction (PCR) requires which temperature to denature DNA?
Answer: D. 94-95 C
Why: PCR denaturation step: DNA is heated to ~94-95 degrees C to separate double-stranded DNA into single strands.
Q32.
Taq polymerase is used in PCR because:
Answer: B. It is thermostable (heat-resistant from Thermus aquaticus bacterium)
Why: Taq polymerase from the thermophilic bacterium Thermus aquaticus is heat-stable, surviving repeated PCR denaturation cycles at 95 C.
Q33.
In Southern blotting, which molecule is being detected?
Answer: C. Specific DNA sequences
Why: Southern blot: DNA is separated by gel electrophoresis, transferred to membrane, then hybridized with a labeled DNA probe to detect specific sequences.
Q34.
Agrobacterium tumefaciens is used in plant biotechnology because:
Answer: B. Its Ti plasmid naturally transfers T-DNA into plant genome (used to insert transgenes)
Why: Agrobacterium Ti (tumor-inducing) plasmid transfers T-DNA into plant cells. Scientists replace pathogenic T-DNA with desired transgenes.
Q35.
The Cas9 protein in CRISPR is guided to its target by:
Answer: B. Guide RNA (gRNA) complementary to the target DNA sequence
Why: CRISPR-Cas9: a guide RNA (gRNA) is designed to match the target DNA sequence. It directs the Cas9 nuclease to cut at that specific location.
Q36.
Tissue culture of plants relies on the concept of:
Answer: B. Totipotency (each plant cell has the potential to develop into a whole organism)
Why: Plant tissue culture exploits totipotency: any plant cell retains the genetic information to develop into a complete plant, given the right hormones and nutrients.
Q37.
Which technique is used to diagnose genetic disorders prenatally?
Answer: B. Amniocentesis and chorionic villus sampling (CVS) -- fetal cells analyzed
Why: Amniocentesis (14-20 weeks): fetal cells from amniotic fluid analyzed. CVS (10-12 weeks): placental cells biopsied. Both allow chromosomal and genetic analysis.
Q38.
Somatic cell nuclear transfer (SCNT) was the technique used for:
Answer: B. Cloning Dolly the sheep
Why: Dolly the sheep (1996) was cloned by SCNT: nucleus from an adult mammary gland cell inserted into enucleated egg cell, then implanted in surrogate ewe.
Q39.
Recombinant DNA is made by:
Answer: B. Cutting DNA with restriction enzymes and joining foreign DNA with ligase
Why: Recombinant DNA: restriction enzymes cut host and foreign DNA; ligase joins them. The resulting hybrid DNA molecule is recombinant DNA.
Q40.
Gene expression can be analyzed across the entire genome using:
Answer: B. DNA microarray (gene chip)
Why: DNA microarray: thousands of probes on a chip hybridize to cDNA from cells, allowing simultaneous measurement of expression of thousands of genes.
Q41.
Antisense technology uses:
Answer: B. RNA complementary to mRNA to block translation of a specific gene
Why: Antisense RNA: sequence complementary to target mRNA. Binds to mRNA, blocking translation or triggering its degradation. Used in gene silencing and therapy.
Q42.
The Flavr Savr tomato was engineered to:
Answer: C. Have delayed ripening and softening (antisense polygalacturonase)
Why: Flavr Savr tomato (1994): first GM food. Antisense gene for polygalacturonase (cell-wall degrading enzyme) introduced, delaying softening and extending shelf life.
Q43.
In forensic DNA profiling, which technique is used to analyze STR loci?
Answer: B. PCR amplification followed by capillary electrophoresis
Why: Forensic DNA profiling: PCR amplifies multiple STR (short tandem repeat) loci. Fragment sizes are measured by capillary electrophoresis. Results create a unique DNA profile.
Q44.
What does the enzyme EcoRI recognise on DNA?
Answer: A. Palindrome sequence
Why: Restriction enzymes recognise palindromic sequences.
Q45.
Sticky ends are produced by which class of enzymes?
Answer: A. Restriction enzymes
Why: Restriction enzymes leave overhanging sticky ends.
Q46.
Which process introduces recombinant DNA into bacteria?
Answer: A. Transformation
Why: Transformation takes up foreign DNA into a host cell.
Q47.
In PCR, which enzyme extends the primers?
Answer: A. Taq polymerase
Why: Thermostable Taq polymerase extends primers in PCR.
Q48.
Selectable markers in a vector help to?
Answer: A. Identify transformants
Why: Markers let us select cells carrying the vector.
Q49.
Which vessel is used for large-scale culture of cells?
Answer: A. Bioreactor
Why: Bioreactors allow large-scale production of products.
Q50.
The ori site in a plasmid is responsible for?
Answer: A. Replication start
Why: The origin of replication controls copy number and replication.
Q51.
Selection of recombinants by insertional inactivation of antibiotic markers is cumbersome. An alternative uses a gene coding for an enzyme that, when intact, cleaves a chromogenic substrate. This selection works because:
Answer: C. Recombinant colonies do not produce colour
Why: If the insert interrupts the enzyme-coding sequence, the enzyme is not produced, so recombinant colonies do not develop colour, while non-recombinants produce a coloured product.
Q52.
In the PCR cycle, the step of annealing requires the temperature to be lowered after denaturation. What happens during annealing?
Answer: D. Primers bind to the complementary single strands
Why: After denaturation separates the strands, the temperature is lowered so that the two sets of primers anneal (hybridise) to the complementary regions of the single strands.
Q53.
Agrobacterium tumefaciens is widely used to deliver genes into plant cells because in nature it:
Answer: A. Transfers a piece of its Ti plasmid DNA into the plant
Why: A. tumefaciens naturally transfers a segment of DNA (T-DNA) from its Ti plasmid into the plant genome, so the disarmed plasmid is used as a vector to deliver desired genes.
Q54.
After a recombinant protein is produced in a bioreactor, it must undergo downstream processing before marketing. This stage involves:
Answer: B. Separation, purification and formulation of the product
Why: Downstream processing includes separation and purification of the product followed by formulation with preservatives and quality control testing before it is marketed.
Q55.
Blunt-ended DNA fragments produced by some restriction enzymes are harder to ligate than sticky ends. Why are sticky ends easier to join?
Answer: C. Their short single-stranded overhangs form hydrogen bonds with complementary ends
Why: Sticky ends have short single-stranded overhangs that base-pair (hydrogen bond) with complementary overhangs, holding the fragments together so DNA ligase can seal them easily.
Q56.
Next-generation sequencing (NGS) differs from Sanger sequencing in:
Answer: B. It sequences millions of DNA fragments simultaneously in parallel (massively parallel sequencing), dramatically reducing cost and time
Why: NGS (Illumina, PacBio, Nanopore): millions of DNA fragments sequenced simultaneously. Much faster and cheaper than Sanger. Used for whole genome sequencing, RNA-seq, ChIP-seq, etc.
Q57.
CRISPR base editing allows:
Answer: B. Precise conversion of one DNA base to another (e.g., C to T or A to G) without double-strand break, reducing off-target indels
Why: Base editors (Komor/Gaudelli): fuse catalytically dead Cas9 (or nickase) with base-modifying enzymes. CBEs: C to T conversion. ABEs: A to G conversion. No DSB needed, fewer indels.
Q58.
ChIP-seq (Chromatin Immunoprecipitation-sequencing) identifies:
Answer: B. Genome-wide protein-DNA interactions and histone modifications (where transcription factors bind, which regions are active)
Why: ChIP-seq: protein cross-linked to DNA, chromatin sheared, antibody pulls down protein-DNA complexes. DNA sequenced to map genome-wide binding sites of transcription factors, histones, etc.
Q59.
mRNA vaccines against COVID-19 work by:
Answer: B. Delivering mRNA encoding the viral spike protein; cells produce the antigen, generating immune response without infection
Why: mRNA vaccines (Pfizer/Moderna): lipid nanoparticles deliver mRNA encoding SARS-CoV-2 spike protein. Cells translate the mRNA, producing spike antigen. Immune system responds, creating memory without live virus.
Q60.
ATAC-seq reveals:
Answer: B. Genome-wide open chromatin regions (accessible, active regulatory elements) by transposase-accessible chromatin with high-throughput sequencing
Why: ATAC-seq: Tn5 transposase cuts and tags accessible (open) chromatin. Sequencing maps genome-wide open chromatin regions, identifying active promoters, enhancers, and regulatory elements.
Q61.
The CRISPR prime editing system (Liu lab, 2019) improves upon base editing by:
Answer: B. Using a pegRNA + Cas9 nickase + reverse transcriptase to install any base change, small insertions or deletions without DSB and without a DNA donor template
Why: Prime editing: pegRNA (guide RNA + desired edit sequence). Cas9 nickase nicks one strand; reverse transcriptase uses pegRNA template to write new sequence. Highly versatile, no DSB.
Q62.
Biosafety level 4 (BSL-4) laboratories are required for:
Answer: B. Work with dangerous pathogens with no treatment or vaccine (Ebola, Marburg, Nipah virus) that are transmitted by aerosol
Why: BSL-4: maximum containment for dangerous, exotic agents (Ebola, Marburg, smallpox). Full-pressure suits or class III biosafety cabinets. Researchers shower on exit. No established treatment.
Q63.
Antibody-drug conjugates (ADCs) are cancer drugs that:
Answer: B. Link a monoclonal antibody (targeting tumor antigen) to a cytotoxic drug, delivering the drug selectively to cancer cells
Why: ADCs: monoclonal antibody + cytotoxic payload linked via a cleavable linker. Antibody targets tumor antigen, delivers drug specifically to cancer cells, reducing systemic toxicity (e.g., ado-trastuzumab emtansine).
Q64.
Single-cell RNA sequencing (scRNA-seq) enables:
Answer: B. Gene expression profiling of individual cells, revealing cellular heterogeneity and cell types within tissues
Why: scRNA-seq: RNA from individual cells is captured, barcoded, and sequenced. Reveals transcriptome of each cell. Identifies rare cell types, transitions, trajectories, and heterogeneity invisible in bulk sequencing.
Q65.
Recombinant adeno-associated virus (rAAV) vectors used in gene therapy are favored because:
Answer: B. They can infect non-dividing cells, have low immunogenicity, and do not typically integrate (episomal expression)
Why: rAAV: small, non-enveloped DNA virus. Infects dividing and non-dividing cells. Usually persists as episome (non-integrating), reducing insertional mutagenesis risk. Multiple serotypes for tissue targeting. Low pathogenicity.
Q66.
Allele-specific oligonucleotide (ASO) hybridization diagnoses:
Answer: B. Single base mutations in specific genes (e.g., sickle cell, cystic fibrosis) by differential hybridization under stringent conditions
Why: ASO hybridization: oligonucleotide probes designed to match wild-type or mutant allele. Under stringent conditions (Tm), only perfect match hybridizes. Used for point mutation diagnosis.
Q67.
Chimeric antigen receptor T (CAR-T) cell therapy works by:
Answer: B. Engineering a patient T cells to express synthetic receptors recognizing tumor antigens, bypassing normal T cell activation requirements
Why: CAR-T: patient T cells engineered to express CARs (antibody fragment + T cell signaling domains). CAR recognizes tumor antigen directly (MHC-independent). Infused cells expand and kill tumor cells.
Q68.
AlphaFold (DeepMind) achievement in biotechnology was:
Answer: B. Solving the protein folding problem by accurately predicting 3D protein structure from amino acid sequence using deep learning
Why: AlphaFold (2020): AI system that predicted protein 3D structure from sequence with near-experimental accuracy. Solved the 50-year protein folding problem. Now provides structures for most known proteins.
Q69.
On-target efficiency vs off-target effects in CRISPR represent:
Answer: B. The balance between desired gene editing at the intended site vs. unintended cuts at similar sequences elsewhere in the genome
Why: CRISPR specificity: on-target = desired edit at correct genomic location. Off-target = unintended cuts at sequences with partial complementarity to gRNA. Reduced by high-fidelity Cas9 variants, paired nickases, or base editors.
Q70.
Which method uses a gene gun to insert DNA?
Answer: A. Biolistics
Why: Biolistics (gene gun) fires DNA-coated particles into cells.
Q71.
Ligating an insert into a plasmid needs matching?
Answer: A. Sticky ends
Why: Complementary sticky ends allow the insert to join the vector.
Q72.
Which bacterium is a natural genetic engineer of plants?
Answer: A. Agrobacterium
Why: Agrobacterium tumefaciens transfers T-DNA into plants.
Q73.
During electrophoresis, DNA migrates toward which pole?
Answer: A. Anode
Why: Negatively charged DNA moves to the positive anode.
Q74.
Downstream processing in biotechnology refers to?
Answer: A. Product recovery
Why: Downstream processing is separation and purification of the product.
Q75.
The disarmed Ti plasmid is obtained from which organism?
Answer: A. Agrobacterium
Why: The Ti plasmid comes from Agrobacterium tumefaciens.