Biotechnology: Principles and Processes (NCERT Practice Paper)
Q1. Which pathogen is used as a vector to deliver 'T-DNA' to transform normal plant cells into a tumor?
Correct Answer: (b)
Agrobacterium tumefaciens is a soil bacterium that causes crown gall disease by transferring a piece of its Ti plasmid (T-DNA) into plant cells. This natural gene transfer ability is harnessed as a plant transformation vector. E. coli, Salmonella, and retroviruses are not used for T-DNA delivery in plants.
Q2. PCR stands for:
Correct Answer: (a)
PCR is the acronym for Polymerase Chain Reaction. It is a technique used to amplify a specific DNA segment exponentially. The other options are incorrect expansions. Understanding the full name is fundamental to molecular biology.
Q3. Match the following for the lac operon genes:
Column I (Gene)
Column II (Product)
A. z gene
(I) Permease
B. y gene
(II) Beta-galactosidase
C. a gene
(III) Transacetylase
Correct Answer: (a)
The lac operon genes: z codes for β‑galactosidase (hydrolyses lactose), y codes for permease (transports lactose), and a codes for transacetylase (modifies lactose derivatives). Thus the correct mapping is z→II, y→I, a→III.
Q4. In 1972, the first recombinant DNA was constructed by linking an antibiotic resistance gene with a native plasmid of:
Correct Answer: (b)
Stanley Cohen and Herbert Boyer performed the landmark experiment in 1972 using a plasmid from Salmonella typhimurium. They inserted an antibiotic resistance gene into this plasmid and introduced it into E. coli, creating the first recombinant DNA. This was a pivotal moment in the birth of genetic engineering. Therefore, the correct organism is Salmonella typhimurium.
Q5. The thermostable DNA polymerase used in PCR is isolated from the bacterium:
Correct Answer: (c)
The DNA polymerase commonly used in PCR is Taq polymerase, isolated from Thermus aquaticus, a bacterium that thrives in hot springs. This enzyme is thermostable, meaning it can withstand the high denaturation temperatures (≈95°C) used in PCR. E. coli and other bacteria do not provide such thermostable polymerases.
Q6. Correct statements about 'Sticky Ends' include: (i) Facilitate the action of DNA ligase. (ii) Form hydrogen bonds with complementary counterparts. (iii) Produced by exonucleases.
Correct Answer: (a)
Sticky ends are single‑stranded overhangs that can hydrogen‑bond to complementary ends, thus facilitating ligation. They are produced by endonucleases (like EcoRI), not exonucleases. So (i) and (ii) are correct, (iii) is false.
Q7. The three steps of each cycle in PCR are:
Correct Answer: (b)
Each PCR cycle consists of three sequential steps: (1) Denaturation – heating to separate DNA strands; (2) Annealing – cooling to allow primers to bind; and (3) Extension – DNA polymerase synthesises new strands. The other options describe other processes (transcription, cloning, RNA processing). Hence, denaturation, annealing, extension is correct.
Q8. Assertion: Ethidium bromide stained gels are exposed to UV light for visualization.
Reason: Purified DNA fragments can be seen clearly in visible light without staining.
Correct Answer: (a)
The assertion is true: ethidium bromide-stained DNA is visualised under UV light. The reason is false: DNA fragments cannot be seen in visible light without staining because DNA itself is colourless and does not absorb visible light. Thus, staining and UV exposure are necessary. So assertion true, reason false.
Q9. Assertion: Thermus aquaticus is used in PCR.
Reason: It provides a DNA polymerase that remains active during high-temperature denaturation.
Correct Answer: (a)
The assertion is true: Taq polymerase from Thermus aquaticus is the enzyme of choice for PCR. The reason is also true and correctly explains the assertion: this polymerase is thermostable, meaning it survives the high denaturation temperatures (~95°C) that would inactivate regular polymerases. This stability is the key reason for using it.
Q10. Select correct statements for 'DNA Polymerases': (i) Use a DNA template to catalyse polymerisation. (ii) Highly efficient and fast. (iii) Rate in E. coli is 2000 bp per second.
Correct Answer: (a)
DNA polymerases synthesise DNA using a template strand. They are highly processive and fast; E. coli DNA polymerase III adds about 2000 nucleotides per second. All three statements are accurate.
Q11. Identify the correct phylum/group being described: (i) It is a sequence from where replication starts. (ii) Controls the copy number of linked DNA. (iii) Essential for any vector.
Correct Answer: (c)
The origin of replication (ori) is the specific sequence where DNA replication initiates. It determines the copy number of the plasmid and is essential for any cloning vector. This matches all three descriptions, so it is the origin of replication.
Q12. Assertion: Bioprocess engineering involves maintaining a sterile ambience.
Reason: Sterile conditions allow the growth of multiple types of microbes in a bioreactor.
Correct Answer: (a)
The assertion is true: bioprocess engineering requires sterile conditions to prevent contamination. However, the reason is false because sterile conditions are meant to allow the growth of only the desired microbe, not multiple types. Contamination by other microbes would be detrimental. So assertion true, reason false.
Q13. The enzyme used to break open bacterial cells to release DNA is:
Correct Answer: (c)
Lysozyme is an enzyme that degrades bacterial cell walls (peptidoglycan), thereby lysing the cells to release their contents, including DNA. Cellulase breaks down cellulose (plant cell walls), chitinase acts on fungal cell walls, and ribonuclease degrades RNA. Thus, lysozyme is used for bacterial lysis.
Q14. Assertion: The 'ori' sequence is responsible for controlling the copy number of linked DNA.
Reason: If one wants many copies, the target DNA should be cloned in a vector with an origin supporting high copy number.
Correct Answer: (a)
The assertion is true: the origin of replication (ori) determines the copy number of the plasmid. The reason is also true and correctly explains the assertion: choosing a vector with a high‑copy‑number ori allows the linked DNA to be amplified manyfold. Therefore, the reason is the correct explanation.
Q15. Identify the correct steps in 'Recombinant DNA Technology': (i) Isolation of DNA. (ii) Ligation of DNA fragment into a vector. (iii) Culturing host cells at large scale. (iv) Downstream processing.
Correct Answer: (a)
The key steps are: isolation of DNA, ligation into a vector, transformation into host, large‑scale culture, and downstream processing. All four are correct steps in recombinant DNA technology, so 'All are correct' is the right choice.
Q16. Identify the correct statements for 'Gel Electrophoresis': (i) Agarose is a natural polymer from sea weeds. (ii) DNA fragments separate according to their size. (iii) Smaller fragments move slower through the gel.
Correct Answer: (a)
Agarose is extracted from seaweed, and it forms a gel that separates DNA by size. However, smaller fragments move faster (farther) through the gel, not slower. So statement (iii) is wrong. Thus, (i) and (ii) are correct.
Q17. Match the following cloning vector components with their roles:
Column I
Column II
A. ori
(I) Identifying non-transformants
B. Selectable marker
(II) Initiation of replication
C. Ligase
(III) Joining DNA ends
Correct Answer: (a)
ori (origin of replication) is the sequence where replication initiates – so A–II. Selectable markers (e.g., antibiotic resistance genes) help in identifying transformed cells, often by eliminating non-transformants – B–I. DNA ligase joins DNA fragments – C–III. Thus, A–II, B–I, C–III is correct.
Q18. Which of the following statements about 'Bioreactors' is true? (i) They provide optimal growth conditions (temp, pH, salts). (ii) The most common type is the stirred-tank. (iii) They process 1 to 10 litres of culture.
Correct Answer: (a)
Bioreactors maintain controlled conditions for growth. The stirred‑tank bioreactor is the most common design. However, they typically process 100–1000 litres, not 1‑10 litres. So (iii) is false. Thus, (i) and (ii) are correct.
Q19. How many restriction enzymes have been isolated from over 230 strains of bacteria?
Correct Answer: (c)
Over 900 restriction enzymes have been identified from more than 230 bacterial strains. This large number reflects the diversity of these enzymes and their importance in molecular biology. The count is well above 500 and not limited to the number of strains. Hence, 'more than 900' is correct.
Q20. Assertion: Agrobacterium tumifaciens is known as 'nature's genetic engineer'.
Reason: It naturally delivers 'T-DNA' to transform normal plant cells into tumor cells.
Correct Answer: (a)
The assertion is true: Agrobacterium is often called nature's genetic engineer because of its ability to transfer DNA to plants. The reason is also true and correctly explains the assertion: it delivers T‑DNA from its Ti plasmid into plant cells, causing tumour formation. This natural property is the basis for its nickname and its use in plant genetic engineering.
Q21. Assertion: Bioreactors have a foam control system.
Reason: Continuous agitation and aeration in a bioreactor can lead to foam formation.
Correct Answer: (a)
The assertion is true: bioreactors are equipped with foam control mechanisms (e.g., mechanical foam breakers or antifoam agents). The reason is also true and correctly explains why foam control is needed: vigorous agitation and aeration generate foam that can overflow or interfere with culture. Thus, the reason is the correct explanation.
Q22. The process including separation and purification of the product is collectively referred to as:
Correct Answer: (b)
Downstream processing encompasses all steps after the biosynthetic phase, including recovery, separation, and purification of the desired product to make it suitable for marketing. Upstream processing refers to the initial stages (e.g., media preparation, fermentation). Transformation is gene transfer, and elution is a specific purification step. So downstream processing is correct.
Q23. Match the following for HGP:
Organism
Base pairs
A. E. coli
(I) 3.3 x 10^9 bp
B. Human (Haploid)
(II) 4.6 x 10^6 bp
Correct Answer: (a)
E. coli has a genome of about 4.6 million base pairs (4.6 x 10⁶ bp) – A–II. The human haploid genome contains approximately 3.3 billion base pairs (3.3 x 10⁹ bp) – B–I. Hence, A–II, B–I is correct.
Q24. Which of the following is considered a selectable marker for E. coli?
Correct Answer: (b)
Selectable markers, such as genes for antibiotic resistance (e.g., ampicillin resistance), allow the identification and selection of transformed cells. The origin of replication is for replication, palindromic sequences are restriction sites, and T‑DNA is used in plant transformation. Hence, ampicillin resistance gene is a selectable marker.
Q25. The primary role of the stirrer in a stirred-tank bioreactor is to:
Correct Answer: (b)
The stirrer (impeller) ensures homogeneous mixing of the culture medium, maintains uniform temperature and nutrient distribution, and enhances oxygen transfer by breaking air bubbles. It does not kill microbes, control temperature directly, or add nutrients (though it disperses added nutrients). Thus, even mixing and oxygen availability is its primary role.
Q26. The process of extracting separated bands of DNA from the agarose gel is called:
Correct Answer: (b)
Elution is the process of extracting DNA from the gel slice after electrophoresis. It involves cutting out the band of interest and purifying the DNA from the agarose. Spooling is used for precipitating DNA, transformation is the uptake of DNA by cells, and ligation is joining DNA fragments. Hence, elution is correct.
Q27. Assertion: Insertional inactivation of $\beta$-galactosidase is used for selection of recombinants.
Reason: Recombinants produce blue coloured colonies in the presence of chromogenic substrate.
Correct Answer: (a)
The assertion is true: insertional inactivation of β‑galactosidase (by cloning a foreign DNA fragment into the lacZ gene) is a common method to distinguish recombinant from non‑recombinant colonies. However, the reason is false: recombinants do not produce blue colour; instead, they produce white colonies because the enzyme is inactivated. Non‑recombinants (with intact lacZ) produce blue colour. So assertion true, reason false.
Q28. Which of the following is correct regarding 'Restriction Enzymes'? (i) Belong to a larger class called nucleases. (ii) Hind II was the first one isolated. (iii) They cut only one strand of the DNA double helix.
Correct Answer: (a)
Restriction enzymes are nucleases that cut DNA. Hind II was the first restriction enzyme discovered. However, they cut both strands of the DNA double helix, not just one. So statement (iii) is false. Hence, only (i) and (ii) are correct.
Q29. Regarding 'Ti Plasmid': (i) Obtained from Agrobacterium tumifaciens. (ii) Modified into a cloning vector. (iii) Still pathogenic to plants.
Correct Answer: (a)
The Ti plasmid comes from Agrobacterium and has been modified to be a non‑pathogenic cloning vector. It is no longer pathogenic after removing the tumour‑inducing genes. Therefore, (i) and (ii) are correct, (iii) is false.
Q30. Which technique enabled the birth of modern biotechnology by allowing the alteration of genetic material?
Correct Answer: (b)
Modern biotechnology is defined by the ability to manipulate genetic material directly. Genetic engineering—the deliberate modification of an organism's genome—is the core technique that distinguishes modern biotechnology from traditional methods. Bioprocess engineering and downstream processing are important but are not the enabling techniques for altering DNA itself.
Q31. Assertion: Stanley Cohen and Herbert Boyer founded the discipline of biotechnology.
Reason: They were the first to recombine segments of DNA and insert them into bacterial cells.
Correct Answer: (a)
The assertion is true: Cohen and Boyer are considered the founders of modern biotechnology for their pioneering work in recombinant DNA. The reason is also true and correctly explains why they are credited: they constructed the first recombinant DNA and introduced it into bacteria, laying the foundation for genetic engineering. Thus, the reason is the correct explanation.
Q32. Match the restriction enzyme with its source organism:
Enzyme
Source
A. EcoRI
(I) Haemophilus influenzae
B. Hind II
(II) Escherichia coli
Correct Answer: (a)
EcoRI is derived from Escherichia coli (strain RY13), so A–II. Hind II is from Haemophilus influenzae, so B–I. Hence, A–II, B–I is the correct matching.
Q33. Identify correct facts for 'Ethidium Bromide': (i) Used to stain DNA in gel. (ii) Shows bright orange bands. (iii) Requires UV light for visualization.
Correct Answer: (a)
Ethidium bromide is a fluorescent dye that intercalates into DNA. Stained DNA appears as bright orange bands under UV light. All three statements are correct.
Q34. The specific sequence of base pairs that reads the same on the two strands when orientation is kept the same is called:
Correct Answer: (b)
A palindromic nucleotide sequence is one where the sequence on one strand reads the same as the complementary strand when read in the same 5' to 3' direction. This property is exploited by restriction enzymes that recognise such sequences. It is not related to replication origins, markers, or sticky ends. Hence, 'palindromic nucleotide sequence' is correct.
Q35. Which of the following phylum/group is being described by the given statements? (i) These are autonomously replicating circular extra-chromosomal DNA. (ii) They are used to multiply alien DNA numbers. (iii) Stanley Cohen and Herbert Boyer used them in 1972.
Correct Answer: (b)
Plasmids are small, circular, extra‑chromosomal DNA molecules that replicate independently. They are widely used as cloning vectors to amplify foreign DNA. The 1972 recombinant DNA experiment used a plasmid from Salmonella typhimurium. Thus, the group described is plasmids.
Q36. Which of the following is correct regarding 'Insertional Inactivation'? (i) Used to differentiate recombinants from non-recombinants. (ii) Based on the ability to produce color with chromogenic substrate. (iii) Recombinants produce blue color.
Correct Answer: (a)
Insertional inactivation (e.g., of lacZ) distinguishes recombinants from non‑recombinants based on colour. Non‑recombinants give blue colonies; recombinants give white. Thus (i) and (ii) are correct, but (iii) is false because recombinants do not produce blue.
Q37. The DNA in a prokaryotic cell is found in a region termed as:
Correct Answer: (b)
Prokaryotes lack a membrane‑bound nucleus; their DNA is concentrated in a region called the nucleoid. Nucleus is eukaryotic, nucleolus is a substructure within the nucleus, and cistron is a genetic term. Therefore, nucleoid is the correct term.
Q38. DNA fragments separated in a gel can be visualized only after staining with:
Correct Answer: (c)
Ethidium bromide is a fluorescent dye that intercalates between DNA base pairs. When exposed to UV light, it emits bright orange fluorescence, allowing DNA bands to be visualised. Bromophenol blue is a loading dye, acetocarmine stains chromosomes, and methylene blue is a general stain but less sensitive. So ethidium bromide is the standard choice.
Q39. Match the following vector types:
A. BAC
Bacterial Artificial Chromosome
B. YAC
Yeast Artificial Chromosome
Correct Answer: (a)
BAC stands for Bacterial Artificial Chromosome, and YAC stands for Yeast Artificial Chromosome. Both are used as cloning vectors to carry large DNA fragments. Since both definitions are correct, the answer is 'Both are correct'.
Q40. Protease is used during DNA isolation to remove:
Correct Answer: (c)
Proteases digest proteins, which are associated with DNA and can contaminate the preparation. This step ensures that the DNA is free from protein contaminants. RNA is removed by ribonuclease, DNA is the target, and polysaccharides are not typically removed by protease. Thus, proteins are removed.
Q41. Enzymes that remove nucleotides from the ends of the DNA are called:
Correct Answer: (b)
Exonucleases remove nucleotides one at a time from the ends of DNA molecules, either from the 5' or 3' terminus. In contrast, endonucleases cut within the DNA strand. Ligases join ends, and polymerases synthesise new strands. Thus, exonucleases are the correct answer.
Q42. The 'rop' gene in vector pBR322 codes for:
Correct Answer: (b)
The rop gene (for replication of plasmid) encodes proteins that regulate the copy number of the plasmid. It is not involved in antibiotic resistance (which is conferred by ampR and tetR), nor does it encode restriction enzymes or selectable markers. Thus, it codes for proteins involved in replication.
Q43. Restriction enzymes are also known as:
Correct Answer: (b)
Restriction enzymes cut DNA at specific sequences, acting like scissors. They are essential tools in genetic engineering for cleaving DNA at defined points. Molecular glue refers to DNA ligase, vectors carry foreign DNA, and selectable markers help identify transformed cells. Hence, 'molecular scissors' is the apt nickname.
Q44. Which are correct for 'Palindromes' in DNA? (i) Read same on both strands when orientation is kept same. (ii) EcoRI sequence is 5'--GAATTC--3'. (iii) Read same as word-palindromes (e.g. MALAYALAM).
Correct Answer: (a)
A palindrome in DNA reads the same on both strands when read in the same 5'→3' orientation. EcoRI recognises GAATTC, which is a palindrome. However, DNA palindromes are not the same as word palindromes; the latter read the same forward and backward on a single strand. So (iii) is false. Thus (i) and (ii) are correct.
Q45. In the nomenclature of EcoRI, the letter 'R' is derived from the name of the:
Correct Answer: (c)
EcoRI is named as: Eco = Escherichia coli, R = strain RY13, I = first enzyme isolated from that strain. The letter 'R' thus indicates the specific bacterial strain, not the genus, species, or scientist. This naming convention is standard for restriction enzymes.
Q46. Match the following for DNA charge and movement:
Term
Description
A. DNA Charge
Negative
B. Movement in Electrophoresis
Towards Anode (positive)
Correct Answer: (a)
DNA is negatively charged due to its phosphate backbone. In gel electrophoresis, it migrates toward the positively charged anode. Both statements are correct, so the answer is 'Both are correct'.
Q47. Match the following bioreactor types:
Column I
Column II
A. Simple stirred-tank
(I) Sterile air bubbles sparged
B. Sparged stirred-tank
(II) Agitator system
Correct Answer: (a)
A simple stirred‑tank bioreactor primarily uses an agitator (stirrer) for mixing – A–II. A sparged stirred‑tank bioreactor additionally has a sparger to introduce sterile air bubbles – B–I. Thus, A–II, B–I is correct.
Q48. Assertion: Recombinant DNA can be forced into a bacterium by heat shock at 42°C.
Reason: Heat shock makes the cell wall impermeable to DNA.
Correct Answer: (c)
The assertion is true: heat shock (a brief exposure to 42°C followed by chilling) is a standard method to make bacteria take up recombinant DNA. However, the reason is false because heat shock makes the cell membrane more permeable (not impermeable) by creating transient pores, allowing DNA to enter. Therefore, the assertion is true but the reason is false.
Q49. Assertion: The DNA polymerase used in PCR is isolated from Thermus aquaticus.
Reason: It is a thermostable enzyme.
Correct Answer: (a)
The assertion is correct: Taq polymerase from Thermus aquaticus is the standard enzyme for PCR. The reason is also true and provides the correct explanation: its thermostability allows it to withstand the high denaturation temperatures without denaturing. This is the key property that makes it suitable for PCR, so the reason is the correct explanation.
Q50. Assertion: Chilled ethanol is used at the final step of DNA isolation.
Reason: DNA precipitates out as fine threads upon addition of ethanol.
Correct Answer: (a)
Both the assertion and reason are true. Chilled ethanol is indeed added to the DNA solution to precipitate DNA, which appears as fine threads. The reason correctly explains why ethanol is used—because DNA is insoluble in alcohol, it precipitates. Hence, the reason is the correct explanation.
Q51. Identify correct features of the 'Sparged Stirred-tank Bioreactor': (i) Sterile air bubbles are sparged. (ii) Dramatic increase in oxygen transfer area. (iii) No agitator system.
Correct Answer: (a)
In a sparged stirred‑tank bioreactor, sterile air is bubbled in (sparged), increasing the surface area for oxygen transfer. It still has an agitator for mixing, so (iii) is false. Thus, (i) and (ii) are correct.
Q52. Match the Following:
A. $\beta$-galactosidase
Enzyme for lactose hydrolysis
B. Taq polymerase
Thermostable DNA polymerase
Correct Answer: (a)
β‑galactosidase hydrolyses lactose into glucose and galactose. Taq polymerase is a thermostable DNA polymerase used in PCR. Both descriptions are accurate, so 'Both are correct'.
Q53. Which enzyme is used to remove RNA during the isolation of DNA?
Correct Answer: (b)
Ribonuclease (RNase) specifically degrades RNA, leaving DNA intact. Protease removes proteins, lysozyme breaks bacterial cell walls, and cellulase degrades cellulose. Thus, to eliminate RNA contamination from DNA preparations, ribonuclease is the appropriate enzyme.
Q54. Which class of enzymes do restriction enzymes belong to?
Correct Answer: (b)
Restriction enzymes are nucleases—enzymes that degrade nucleic acids. They cleave the phosphodiester bonds within DNA strands. Ligases join DNA fragments, polymerases synthesise DNA, and hydrolases catalyse hydrolysis of various bonds. Therefore, nucleases is the correct class.
Q55. If any protein encoding gene is expressed in a heterologous host, it is called a:
Correct Answer: (b)
When a gene from one organism is cloned and expressed in another (heterologous) host, the resulting protein is termed a recombinant protein. It is not naturally produced in that host. Synthetic proteins are chemically synthesised, and hybrid proteins are fusions. Thus, recombinant protein is correct.
Q56. Correct features of 'DNA Polymorphism': (i) Basis of genetic mapping. (ii) Variation at genetic level arises due to mutations. (iii) Frequency must be greater than 0.01 in human population.
Correct Answer: (a)
DNA polymorphism is variation in DNA sequence that is the basis of genetic mapping. It arises from mutations, and to be considered polymorphic, its frequency must be >1% (0.01) in a population. All three statements are correct.
Q57. Match the PCR steps with their functions:
Step
Purpose
A. Denaturation
(I) DNA polymerase adds nucleotides
B. Annealing
(II) Primers bind to template
C. Extension
(III) Separating DNA strands using heat
Correct Answer: (a)
Denaturation uses high temperature to separate the two DNA strands – A–III. Annealing allows primers to bind to complementary sequences – B–II. Extension is when the polymerase synthesises new DNA – C–I. So A–III, B–II, C–I is correct.
Q58. To produce large quantities of biotechnological products, vessels called ______ are used.
Correct Answer: (b)
Bioreactors are vessels designed for the large‑scale cultivation of microorganisms or cells to produce biotechnological products. They provide optimal conditions for growth and product formation. Fermentors are a type of bioreactor specifically for fermentation, incubators are for small‑scale growth, and centrifuges are for separation. Hence, bioreactors is the general term.
Q59. Which method of gene transfer is suitable for plants using high-velocity micro-particles of gold or tungsten?
Correct Answer: (b)
Biolistics, also known as the gene gun method, uses high‑velocity micro‑particles (gold or tungsten) coated with DNA to bombard plant cells, delivering the DNA into the cells. Micro‑injection is for animal cells, heat shock is for bacteria, and disarmed pathogens are used in Agrobacterium-mediated transformation. Therefore, biolistics is the correct method.
Q60. The European Federation of Biotechnology (EFB) definition of biotechnology encompasses:
Correct Answer: (c)
The EFB definition is broad and includes both the traditional techniques (like fermentation) and the modern molecular approaches (genetic engineering, cell culture, etc.). This inclusive view recognises that biotechnology has evolved from age-old practices to cutting-edge genetic manipulation, and both are integral to the field. Thus, the correct choice is the one that covers both aspects.
Q61. The specific DNA sequence in a chromosome which is responsible for initiating replication is called:
Correct Answer: (c)
The origin of replication (ori) is a defined DNA sequence where replication begins. It is essential for any DNA molecule to be replicated and maintained in a host cell. Promoters are for transcription, terminators end transcription, and recognition sequences are for restriction enzymes. Thus, 'origin of replication' is the correct term.
Q62. Match the scientist with their discovery:
Column I
Column II
A. Herbert Boyer
(I) Plasmids
B. Stanley Cohen
(II) Restriction enzymes / Sticky ends
C. Frederick Sanger
(III) Amino acid sequencing
Correct Answer: (a)
Herbert Boyer is known for his work on restriction enzymes (EcoRI) and the concept of sticky ends – A–II. Stanley Cohen studied plasmids and their use as cloning vectors – B–I. Frederick Sanger developed methods for sequencing proteins (and later DNA) – C–III. Thus, A–II, B–I, C–III is correct.
Q63. Purified DNA precipitates out after the addition of:
Correct Answer: (b)
DNA is insoluble in alcohol, especially cold ethanol. When chilled ethanol is added to a DNA solution, the DNA precipitates out as fine white threads. This is a standard step in DNA isolation to concentrate and purify the nucleic acid. Warm water, HCl, or ether do not precipitate DNA in this manner.
Q64. Regarding 'PCR', identify the correct statements: (i) Used for amplification of gene of interest. (ii) Primers are small chemically synthesised oligonucleotides. (iii) Taq polymerase is sensitive to high temperatures.
Correct Answer: (a)
PCR amplifies a specific gene. Primers are short synthetic oligonucleotides. However, Taq polymerase is thermostable, not sensitive to high temperatures; it withstands them. So (iii) is false, leaving (i) and (ii) correct.
Q65. Match the enzymes in Column I with their target substrates in Column II:
Column I (Enzyme)
Column II (Substrate)
A. Lysozyme
(I) Plant cells
B. Cellulase
(II) Fungus
C. Chitinase
(III) Bacteria
Correct Answer: (a)
Lysozyme breaks down bacterial cell walls (peptidoglycan) – so A matches III. Cellulase hydrolyses cellulose in plant cell walls – B matches I. Chitinase degrades chitin, a component of fungal cell walls – C matches II. This correct pairing is reflected in option A–III, B–I, C–II.
Q66. Regarding 'pBR322', which statements are correct? (i) It is an E. coli cloning vector. (ii) It has antibiotic resistance genes ampR and tetR. (iii) 'rop' codes for the proteins involved in replication.
Correct Answer: (a)
pBR322 is a widely used E. coli cloning vector. It contains genes for resistance to ampicillin (ampR) and tetracycline (tetR). The rop gene encodes proteins that regulate plasmid copy number (replication). All three statements are correct.
Q67. Which of the following is correct? (i) DNA replication results into polyploidy if cell division fails. (ii) Biotechnology products include antibiotics, vaccines, enzymes. (iii) DNA is a hydrophilic molecule.
Correct Answer: (a)
If DNA replication occurs without cell division, it can lead to polyploidy. Biotechnology produces antibiotics, vaccines, and enzymes. DNA is hydrophilic due to its sugar‑phosphate backbone. All statements are true.
Q68. Assertion: A vector must have very few recognition sites.
Reason: Multiple recognition sites within a vector generate several fragments, complicating gene cloning.
Correct Answer: (a)
The assertion is true: a cloning vector should ideally have a single recognition site for a given restriction enzyme to ensure linearisation. The reason is also true and correctly explains the assertion: multiple sites would cause the vector to be cut into many fragments, making it difficult to clone a single insert. So the reason is the correct explanation.
Q69. The average size of a human cell DNA is 2.2 metres, while the dimension of a typical nucleus is approximately:
Correct Answer: (b)
The nucleus of a typical human cell is about 10⁻⁶ metres (about 10 micrometres) in diameter. DNA is highly compacted to fit into this tiny space. The values 10⁻³ m (millimetre) is too large, 10⁻⁹ m (nanometre) is too small (molecular scale), and 10⁻¹² m is atomic. Therefore, 10⁻⁶ m is the correct order of magnitude.
Q70. The first restriction endonuclease to be isolated and characterized was:
Correct Answer: (c)
Hind II was the first restriction endonuclease to be isolated and characterised. It was discovered in Haemophilus influenzae and recognises a specific six-base-pair sequence. EcoRI, BamHI, and PstI were discovered later. Therefore, Hind II holds the distinction of being the first.
Q71. Which of the following have the ability to replicate within bacterial cells independent of chromosomal DNA control?
Correct Answer: (c)
Both plasmids and bacteriophages are autonomously replicating genetic elements in bacteria. Plasmids are extrachromosomal circular DNA, while bacteriophages are viruses that replicate using bacterial machinery. Both can exist and replicate independently of the bacterial chromosome. Therefore, both are correct.
Q72. To make bacterial cells 'competent' to take up DNA, they are treated with a specific concentration of a divalent cation such as:
Correct Answer: (b)
Treatment with divalent cations like calcium (Ca²⁺) at specific concentrations increases the permeability of bacterial cell membranes, making them competent for transformation. This is a standard procedure for introducing recombinant DNA into bacteria. Magnesium, potassium, and sodium are not used for this purpose.
Q73. Identify true statements for 'Selectable Markers': (i) Help in identifying transformants. (ii) Help in eliminating non-transformants. (iii) Genes for antibiotic resistance are commonly used.
Correct Answer: (a)
Selectable markers are used to identify transformants and eliminate non‑transformants, often using antibiotic resistance genes. All three statements are true, so 'All are correct'.
Q74. The presence of a chromogenic substrate gives ______ coloured colonies if the plasmid does not have an insert.
Correct Answer: (b)
In blue-white screening, a chromogenic substrate (like X-gal) is cleaved by β-galactosidase to produce a blue product. If the plasmid carries an insert within the lacZ gene, β-galactosidase is inactivated and colonies remain white. Therefore, non‑recombinants (no insert) form blue colonies.
Q75. Match the Following:
Term
Unit
A. Bioreactor volume
100-1000 litres
B. PCR amplification
1 billion copies
Correct Answer: (a)
Bioreactors typically operate at volumes of 100–1000 litres for large‑scale production. PCR can amplify a single DNA molecule to about a billion (10⁹) copies. Both statements are correct, so the answer is 'Both correct'.
Q76. Match the following gene transfer methods:
Column I
Column II
A. Micro-injection
(I) Plant cells (gold/tungsten)
B. Biolistics
(II) Animal cell nucleus
C. Disarmed pathogen
(III) Agrobacterium / Retrovirus
Correct Answer: (a)
Micro‑injection is used to inject DNA directly into the nucleus of animal cells – A–II. Biolistics (gene gun) bombards plant cells with DNA‑coated gold/tungsten particles – B–I. Disarmed pathogens, such as modified Agrobacterium or retroviruses, are used as vectors to deliver DNA – C–III. So A–II, B–I, C–III is correct.
Q77. Match the following for transformation markers:
A. Insertional inactivation
Selection of recombinants
B. Chromogenic substrate
Color-based selection
Correct Answer: (a)
Insertional inactivation (e.g., disruption of lacZ) is indeed used to select recombinants by colour difference. Chromogenic substrates like X‑gal enable colour‑based selection. Both statements are accurate, so 'Both are correct' is the answer.
Q78. Regarding the 'First Recombinant DNA' (1972): (i) Constructed by Stanley Cohen and Herbert Boyer. (ii) Involved Salmonella typhimurium plasmid. (iii) Used DNA ligase to link genes.
Correct Answer: (a)
The first recombinant DNA was indeed made by Cohen and Boyer. They used a plasmid from Salmonella typhimurium and linked an antibiotic resistance gene to it using DNA ligase. All three statements are correct.
Q79. Select correct statements for 'Downstream Processing': (i) Includes separation and purification. (ii) Product is formulated with preservatives. (iii) It is done before biosynthetic stage.
Correct Answer: (a)
Downstream processing involves separation and purification, and the final product is often formulated with preservatives for stability. However, it is done after the biosynthetic stage, not before. Therefore, (i) and (ii) are correct.
Q80. Assertion: DNA cannot pass through cell membranes.
Reason: DNA is a hydrophilic molecule.
Correct Answer: (a)
DNA is highly hydrophilic due to its charged phosphate backbone and sugar groups. This prevents it from crossing the hydrophobic lipid bilayer of cell membranes without assistance. The assertion is correct, and the reason correctly explains why DNA cannot pass through membranes—because of its hydrophilic nature.
Q81. Assertion: A plasmid is autonomously replicating circular extra-chromosomal DNA.
Reason: Plasmids are always found in all eukaryotic cells.
Correct Answer: (a)
The assertion is correct: plasmids are small, circular DNA molecules that replicate independently of the chromosomal DNA. However, the reason is false because plasmids are primarily found in bacteria, not in all eukaryotic cells (they are rare in eukaryotes). Thus, the assertion is true but the reason is false.
Q82. Which of the following is true for 'Transformation'? (i) It is a procedure to introduce alien DNA into a host. (ii) Bacterial cells must be made competent using calcium. (iii) It is achieved by incubating cells with DNA on ice, followed by 42°C heat shock.
Correct Answer: (a)
Transformation is the uptake of foreign DNA by a cell. Bacteria are made competent by treatment with calcium ions. The DNA is then incubated with cells on ice, followed by a heat shock at 42°C to facilitate entry. All three statements are accurate.
Q83. In which method is recombinant DNA directly injected into the nucleus of an animal cell?
Correct Answer: (c)
Micro-injection involves the direct physical insertion of recombinant DNA into the nucleus of an animal cell using a fine glass needle. Biolistics/gene gun uses high-velocity particles for plant cells, and heat shock is used for bacterial transformation. Therefore, micro-injection is the correct method.
Q84. Hind II always cuts DNA molecules at a particular point by recognizing a specific sequence of:
Correct Answer: (b)
Hind II recognises a specific sequence of six base pairs. The recognition site is palindromic and is cut within that sequence. Most restriction enzymes recognise sequences of 4 to 8 base pairs; Hind II's specificity is six base pairs. Therefore, the correct answer is 6 base pairs.
Q85. Assertion: DNA ligase is referred to as 'molecular scissors'.
Reason: It helps in joining the cut ends of DNA molecules.
Correct Answer: (a)
The assertion is false: DNA ligase is not called molecular scissors; that term is used for restriction enzymes (which cut DNA). The reason is true: DNA ligase does join DNA fragments. However, the assertion and reason contradict each other because ligase is not scissors. Therefore, the answer is 'assertion false but reason true'.
Q86. Which statements regarding 'DNA Isolation' are true? (i) Proteins removed by protease. (ii) RNA removed by ribonuclease. (iii) Purified DNA is seen as fine threads in chilled ethanol.
Correct Answer: (a)
During DNA isolation, proteins are digested by protease, RNA is degraded by ribonuclease, and DNA precipitates as fine threads upon addition of chilled ethanol. All three steps are standard, so all statements are correct.
Q87. Regarding 'HGP' methodologies: (i) ESTs focus on identifying genes expressed as RNA. (ii) Sequence Annotation involves sequencing all coding and non-coding parts. (iii) BAC and YAC were used as vectors.
Correct Answer: (a)
ESTs (Expressed Sequence Tags) identify genes transcribed into RNA. Sequence annotation is the process of attaching biological information to sequences, not sequencing. BAC and YAC were indeed used as vectors in the Human Genome Project. All three statements are correct.
Q88. Assertion: Recombination is the generation of non-parental gene combinations.
Reason: Linkage describes the physical association of genes on a chromosome.
Correct Answer: (a)
Both statements are true. Recombination indeed produces new combinations of alleles not found in parents. Linkage refers to genes being located on the same chromosome. However, linkage does not explain the generation of new combinations; in fact, linkage tends to keep genes together. So both are true, but the reason is not the correct explanation.
Q89. Assertion: Traditional hybridization often leads to inclusion of undesirable genes.
Reason: Genetic engineering allows the isolation and introduction of only desirable genes.
Correct Answer: (b)
Both statements are true. Traditional hybridisation involves crossing entire genomes, which can bring in unwanted traits along with the desired ones. Genetic engineering, in contrast, allows precise transfer of only the gene of interest. However, the reason does not explain why traditional hybridisation leads to undesirable genes; it merely contrasts the two methods. So both are true, but reason is not the correct explanation.
Q90. Match the Following:
Term
Description
A. Palindrome
(I) Overhanging DNA stretches
B. Sticky ends
(II) Reads same forward/backward
C. Elution
(III) Extraction of DNA from gel
Correct Answer: (a)
A palindrome in DNA is a sequence that reads the same on both strands – A–II. Sticky ends are the single‑stranded overhangs produced by restriction enzymes – B–I. Elution is the extraction of DNA from agarose gel – C–III. Thus, A–II, B–I, C–III is correct.
Q91. Assertion: Palindromes in DNA read the same on both strands when orientation is kept same.
Reason: EcoRI recognizes the sequence GAATTC.
Correct Answer: (a)
Both statements are true: palindromic sequences read the same on both strands, and EcoRI recognises GAATTC (which is a palindrome). However, the example does not explain the general definition of palindromes; it merely gives an instance. So both are true, but the reason is not the correct explanation.
Q92. Assertion: Downstream processing involves separation and purification.
Reason: It is done before the product is ready for marketing.
Correct Answer: (b)
The assertion is true: downstream processing indeed includes separation and purification of the product. The reason is also true: downstream processing occurs after the biosynthetic stage and is necessary before the product is ready for marketing. However, the reason does not explain the content of downstream processing; it only states when it happens. Therefore, both are true but the reason is not the correct explanation.
Q93. The overhanging single-stranded portions left after restriction enzyme action are called:
Correct Answer: (b)
When restriction enzymes cut DNA in a staggered manner, they leave short, single-stranded overhangs called sticky ends. These can base-pair with complementary sticky ends, aiding in the joining of DNA fragments. Blunt ends have no overhang, satellite DNA is repetitive, and exons are coding regions. Thus, sticky ends is the correct term.
Q94. Waiters on the 'sticky ends' of DNA form ______ bonds with their complementary counterparts.
Correct Answer: (c)
The single‑stranded overhangs of sticky ends can base‑pair with complementary overhangs through hydrogen bonds between the complementary bases. These hydrogen bonds are non‑covalent and transient, allowing the fragments to anneal. Later, DNA ligase seals the nicks with covalent phosphodiester bonds. Thus, hydrogen bonds are formed initially.
Q95. DNA fragments are negatively charged and can be separated by forcing them to move towards the:
Correct Answer: (b)
Because DNA molecules carry a net negative charge due to their phosphate backbone, they migrate towards the positively charged electrode (anode) during electrophoresis. The cathode is negative, and the matrix and well are not electrodes. Therefore, anode is the correct direction.
Q96. Assertion: In gel electrophoresis, smaller DNA fragments move farther than larger ones.
Reason: The agarose gel provides a sieving effect based on size.
Correct Answer: (a)
The assertion is correct: smaller DNA fragments migrate faster and thus travel farther through the gel. The reason is also true: the agarose gel acts as a molecular sieve, allowing smaller molecules to pass through more easily. The reason correctly explains why smaller fragments move farther, as the sieving effect separates based on size.
Q97. Which of the following is correct? (i) Herbert Boyer studied restriction enzymes in E. coli. (ii) Stanley Cohen studied plasmids. (iii) They met in Hawaii in 1969.
Correct Answer: (a)
Boyer worked on restriction enzymes (EcoRI), Cohen studied plasmids, and they met at a conference in Hawaii in 1969, leading to their collaboration. All three statements are historically accurate.
Q98. Which are correct for 'Biolistics'? (i) Also called gene gun. (ii) Uses gold or tungsten micro-particles. (iii) Recombinant DNA is directly injected into the nucleus.
Correct Answer: (a)
Biolistics is also known as the gene gun method. It uses high‑velocity gold or tungsten particles coated with DNA. The DNA is not injected directly; that is micro‑injection. So (i) and (ii) are correct, (iii) is false.
Q99. The most commonly used matrix in gel electrophoresis is agarose, which is a natural polymer extracted from:
Correct Answer: (b)
Agarose is a polysaccharide derived from red algae (seaweeds). It forms a gel that acts as a molecular sieve for separating DNA fragments. It is not obtained from fungi, bacteria, or animal tissues. Thus, 'sea weeds' is the correct source.
Q100. The genetic material of all organisms without exception is:
Correct Answer: (d)
All organisms use nucleic acids (either DNA or RNA) as their genetic material. While most organisms have DNA, some viruses use RNA, so the universal genetic material is nucleic acid. DNA is not universal (RNA viruses), RNA is not universal (all cells have DNA), and proteins are not genetic material. Hence, nucleic acid is the correct answer.