CUET UG Categorised PYQ Biology Unit 9 -

📚

CUET UG Categorised PYQ Biology Unit 9

BIOLOGY

⏱️ 30 Minutes

❓ 31 Questions

📅 2022, 2023, 2024 & 2025

✍️ Long Answers

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Categorised PYQ Biology Unit 9

1 / 31

QUESTION 1 OF 31

📄 Passage

The cutting of DNA by restriction endonucleases results in fragments of DNA. These fragments can be separated by a technique known as gel electrophoresis. Since DNA fragments are negatively charged molecules, they can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. The commonly used matrix is agarose which is a natural polymer extracted from sea weeds. The DNA fragments separate according to their size through sieving effect provided by the agarose gel. Hence, the smaller fragments move farther in the agarose gel. The separated DNA fragments can be visualised only after staining the DNA with ethidium bromide followed by exposure to UV radiation. Bright orange coloured bands of DNA can be observed. The separated bands of DNA are cut out from the agarose gel and extracted from the gel piece. This step is known as elution. The DNA fragments purified in this way are used in constructing recombinant DNA by joining them with cloning vectors.

Agarose is extracted from ______. (PYQ 2022 Shift 1)

Answer Review

📄 Passage

Agarose is extracted from ______. (PYQ 2022 Shift 1)

A Bacteria

B Marine animals

C Sea weeds

D Fungi

💡 Short Explanation

Agarose is a natural polymer. Obtained from seaweeds. Used in gel electrophoresis.

✅ Correct Answer Explanation

Agarose is extracted from seaweeds and forms the gel matrix used in electrophoresis for separation of DNA fragments.

❓ Why Other Options Are Incorrect

Option A) Not source of agarose.
Option B) Not source of agarose.
Option D) Not source of agarose.

🎯 Strategy

Used: NCERT Recall

Option A → Incorrect.
Option B → Incorrect.
Option C → Correct.
Option D → Incorrect.

Final Answer → Sea weeds.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Gel Electrophoresis.

📄 Passage

What is elution? (PYQ 2022 Shift 1)

A Its movement of negatively charged DNA fragments through agarose gel

B Extraction of DNA from the host

C Extraction of DNA and treatment with restriction endonuclease

D Cutting of separated DNA fragments from agarose gel and extraction of DNA fragments

💡 Short Explanation

DNA bands are excised. DNA is recovered from gel. This step is called elution.

✅ Correct Answer Explanation

After electrophoresis, the desired DNA band is cut from the agarose gel and DNA is extracted from the gel piece. This process is called elution.

❓ Why Other Options Are Incorrect

Option A) Describes electrophoresis.
Option B) Incomplete definition.
Option C) Restriction digestion step.

🎯 Strategy

Used: NCERT Recall

Option A → Electrophoresis.
Option B → Incorrect.
Option C → Different process.
Option D → Correct.

Final Answer → Option D.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Elution.

📄 Passage

The DNA fragments formed by treatment with endonucleases are separated by ______. (PYQ 2022 Shift 1)

A PCR

B Gel electrophoresis

C Cloning

D Restriction digestion

💡 Short Explanation

DNA fragments differ in size. Gel electrophoresis separates them. Uses agarose matrix.

✅ Correct Answer Explanation

Restriction endonucleases cut DNA into fragments. These fragments are then separated according to size using gel electrophoresis.

❓ Why Other Options Are Incorrect

Option A) Amplifies DNA.
Option C) Produces recombinant DNA.
Option D) Creates fragments but does not separate them.

🎯 Strategy

Used: NCERT Recall

Option A → Amplification.
Option B → Correct.
Option C → Recombinant DNA.
Option D → Cutting step.

Final Answer → Gel electrophoresis.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Gel Electrophoresis.

📄 Passage

The separated DNA fragments can be visualised after staining with ______ followed by exposure to UV radiation. (PYQ 2022 Shift 1)

A β-galactosidase, UV radiation

B β-galactosidase, Gamma radiation

C Ethidium bromide, UV radiation

D Ethidium bromide, Gamma radiation

💡 Short Explanation

Ethidium bromide binds DNA. UV light reveals bands. Orange fluorescent bands appear.

✅ Correct Answer Explanation

DNA bands become visible after staining with ethidium bromide and exposing the gel to UV radiation, producing bright orange fluorescent bands.

❓ Why Other Options Are Incorrect

Option A) β-galactosidase is an enzyme.
Option B) Incorrect stain and radiation.
Option D) UV, not gamma radiation, is used.

🎯 Strategy

Used: NCERT Recall

Option A → Incorrect.
Option B → Incorrect.
Option C → Correct.
Option D → Wrong radiation.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, DNA Visualization.

📄 Passage

The fragments of DNA separate on agarose gel, based on the ______. (PYQ 2022 Shift 1)

A Size of fragments

B Charge of each fragment

C Colour of fragment

D Type of DNA

💡 Short Explanation

Agarose acts as molecular sieve. Smaller fragments move faster. Separation depends on size.

✅ Correct Answer Explanation

Although DNA fragments are negatively charged, their separation in agarose gel occurs primarily according to size because the gel acts as a molecular sieve. Smaller fragments move farther than larger ones.

❓ Why Other Options Are Incorrect

Option B) All DNA fragments possess similar charge-to-mass characteristics.
Option C) DNA has no role of colour in separation.
Option D) Separation is not based on DNA type.

🎯 Strategy

Used: NCERT Recall

Option A → Correct.
Option B → Common trap.
Option C → Irrelevant.
Option D → Irrelevant.

Final Answer → Size of fragments.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Agarose Gel Electrophoresis.

6 Identify the enzyme used for the isolation of genetic material from fungal cells: (PYQ 2023 Shift 1)

A Lysozyme

B Pepsin

C Cellulase

D Chitinase

💡 Short Explanation

Fungal cell wall contains chitin. Chitinase digests chitin. DNA can then be isolated.

✅ Correct Answer Explanation

The fungal cell wall is primarily composed of chitin. Chitinase breaks down chitin, enabling the release and isolation of genetic material from fungal cells.

❓ Why Other Options Are Incorrect

Option A) Lysozyme acts on bacterial cell walls.
Option B) Digestive enzyme for proteins.
Option C) Cellulose digestion, mainly plant cell walls.

🎯 Strategy

Used: Elimination

Option A → Bacteria.
Option B → Protein digestion.
Option C → Plants.
Option D → Fungi.

Final Answer → Chitinase.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Isolation of DNA.

7 Arrange the steps of PCR in correct sequence: (PYQ 2023 Shift 1)
(A) Annealing of primers
(B) Amplified DNA
(C) Denaturation of DNA
(D) Extension of primers

A (A), (C), (B), (D)

B (D), (A), (C), (B)

C (C), (A), (D), (B)

D (C), (B), (D), (A)

💡 Short Explanation

DNA denatures first. Primers anneal. DNA synthesis occurs. Amplified product forms.

✅ Correct Answer Explanation

PCR begins with denaturation of DNA strands. Primers then anneal to target sequences. DNA polymerase extends primers to synthesize new strands. Repeated cycles generate amplified DNA.

❓ Why Other Options Are Incorrect

Option A) Annealing cannot precede denaturation.
Option B) Extension before denaturation is impossible.
Option D) Amplified DNA cannot appear before synthesis.

🎯 Strategy

Used: Contextual/Tonal Matching

Option A → Wrong order.
Option B → Wrong order.
Option C → Correct PCR cycle.
Option D → Product placed too early.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, PCR.

8 Match the following: (PYQ 2023 Shift 1)

List I	List II
A. Plasmid of Salmonella	I. Join foreign DNA to plasmid
B. Restriction enzymes	II. Insertional inactivation
C. Ligase	III. Construction of recombinant DNA
D. β-galactosidase	IV. Molecular scissors

A (A)-(II), (B)-(III), (C)-(I), (D)-(IV)

B (A)-(III), (B)-(IV), (C)-(I), (D)-(II)

C (A)-(IV), (B)-(I), (C)-(III), (D)-(II)

D (A)-(III), (B)-(II), (C)-(IV), (D)-(I)

💡 Short Explanation

Restriction enzymes = molecular scissors. Ligase joins DNA fragments. β-galactosidase used in insertional inactivation.

✅ Correct Answer Explanation

Salmonella plasmids are used in recombinant DNA construction. Restriction enzymes cut DNA and are called molecular scissors. Ligase joins DNA fragments. β-galactosidase acts as a marker in insertional inactivation.

❓ Why Other Options Are Incorrect

Option A) Restriction enzyme incorrectly matched.
Option C) Ligase and plasmid mismatched.
Option D) Multiple wrong associations.

🎯 Strategy

Used: Option Grouping

Option A → Incorrect.
Option B → Correct.
Option C → Incorrect.
Option D → Incorrect.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Recombinant DNA Technology.

9 The steps of DNA fingerprinting are given below. Arrange them in a correct sequence. (PYQ 2023 Shift 2)
(A) Separation of DNA fragments by electrophoresis
(B) Hybridisation using labelled VNTR probe
(C) Isolation and digestion of DNA
(D) Detection of hybridised DNA fragments by autoradiography
(E) Transferring of separated DNA fragments to synthetic membranes

A (C), (B), (A), (E), (D)

B (A), (C), (D), (B), (E)

C (C), (A), (E), (B), (D)

D (B), (E), (D), (A), (C)

💡 Short Explanation

DNA isolation first. Electrophoresis separates fragments. Probe hybridization occurs before autoradiography.

✅ Correct Answer Explanation

The sequence of DNA fingerprinting is: Isolation and digestion of DNA → Separation of DNA fragments by electrophoresis → Transfer to membrane (Southern blotting) → Hybridisation with labelled VNTR probe → Detection by autoradiography.

❓ Why Other Options Are Incorrect

Option A) Hybridisation cannot occur before electrophoresis.
Option B) DNA must be isolated before separation.
Option D) Starts with hybridisation, which is impossible.

🎯 Strategy

Used: Contextual/Tonal Matching

Option A → Wrong sequence.
Option B → Wrong sequence.
Option C → Correct sequence.
Option D → Completely incorrect.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, DNA Fingerprinting.

10 Arrange the following steps of gel electrophoresis in correct sequence: (PYQ 2023 Shift 2)
(A) Staining the DNA with ethidium bromide
(B) Movement of DNA fragments towards anode under an electric field through agarose
(C) Exposure to UV radiation
(D) Separation of DNA fragments according to their size

A (B), (D), (A), (C)

B (C), (A), (D), (B)

C (B), (A), (C), (D)

D (A), (D), (B), (C)

💡 Short Explanation

DNA first migrates. Fragments separate by size. Ethidium bromide staining follows. UV reveals bands.

✅ Correct Answer Explanation

DNA fragments move through agarose gel under electric current. Smaller fragments move faster, producing separation by size. The gel is then stained with ethidium bromide and visualized under UV light.

❓ Why Other Options Are Incorrect

Option B) UV cannot precede electrophoresis.
Option C) Separation occurs before staining.
Option D) Staining cannot occur first.

🎯 Strategy

Used: Contextual/Tonal Matching

Option A → Correct sequence.
Option B → Incorrect.
Option C → Incorrect.
Option D → Incorrect.

Final Answer → Option A.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Gel Electrophoresis.

11 If a scientist wants to recover many copies of the target DNA through recombinant DNA technology, what augmentation need to be done in cloning vector? (PYQ 2023 Shift 2)

A Reduce cloning sites

B Add origin of replication (ori) that support high copy number

C Add more selectable marker

D Add more cloning sites

💡 Short Explanation

ori controls replication. High-copy ori gives more DNA copies. Essential for amplification.

✅ Correct Answer Explanation

The origin of replication determines how many copies of a vector are produced in a host cell. High-copy-number origins generate large quantities of recombinant DNA.

❓ Why Other Options Are Incorrect

Option A) Reduces utility.
Option C) Marker does not increase copy number.
Option D) Cloning sites do not affect replication.

🎯 Strategy

Used: Elimination

Option A → Incorrect.
Option B → Correct.
Option C → Selection only.
Option D → Cloning convenience only.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Cloning Vectors.

12 The cell wall of a bacteria can be removed by treated it with enzyme: (PYQ 2023 Shift 2)

A Lysozyme

B Cellulase

C Chitinase

D Pectinase

💡 Short Explanation

Bacterial wall contains peptidoglycan. Lysozyme digests peptidoglycan. Used for DNA isolation.

✅ Correct Answer Explanation

Lysozyme breaks down peptidoglycan, the main component of bacterial cell walls. This allows release of cellular contents including DNA.

❓ Why Other Options Are Incorrect

Option B) Digests cellulose.
Option C) Digests chitin.
Option D) Digests pectin.

🎯 Strategy

Used: Elimination

Option A → Bacteria.
Option B → Plants.
Option C → Fungi.
Option D → Plant middle lamella.

Final Answer → Lysozyme.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Isolation of DNA.

13 The gene encoding resistance to which antibiotic are considered useful selectable marker for E. coli? (PYQ 2023 Shift 2)
A) Ampicillin
B) Tetracycline
C) Kanamycin
D) Penicillin
E) Chloramphenicol

A (A) and (D) only

B (B) and (C) only

C (C) and (D) only

D (A), (B), (C) and (E) only

💡 Short Explanation

Common selectable markers in vectors. Ampicillin, tetracycline, kanamycin and chloramphenicol resistance genes used. Penicillin resistance marker is not typically used.

✅ Correct Answer Explanation

Selectable marker genes help identify transformed bacteria. Common markers used in E. coli vectors include resistance genes for ampicillin, tetracycline, kanamycin and chloramphenicol.

❓ Why Other Options Are Incorrect

Option A) Excludes valid markers.
Option B) Incomplete set.
Option C) Includes penicillin incorrectly.

🎯 Strategy

Used: NCERT Recall

Option A → Incomplete.
Option B → Incomplete.
Option C → Includes wrong marker.
Option D → Correct.

Final Answer → Option D.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Selectable Markers.

14 Arrange the given steps of DNA fingerprinting technique in correct sequence. (PYQ 2023 Shift 3)
(A) Isolation of DNA and digestion by restriction endonuclease
(B) Separation of DNA fragments by electrophoresis
(C) Hybridisation with labelled VNTR probe and autoradiography
(D) Blotting of separated DNA fragments by autoradiography

A A, C, B, D

B A, B, D, C

C D, B, A, C

D A, B, C, D

💡 Short Explanation

DNA isolation occurs first. Fragments separated by electrophoresis. Southern blotting precedes hybridisation.

✅ Correct Answer Explanation

Correct sequence: 1. Isolation and restriction digestion of DNA. 2. Electrophoretic separation of fragments. 3. Blotting onto membrane (Southern blotting). 4. Hybridisation with labelled VNTR probe followed by autoradiography. Therefore the correct order is A → B → D → C.

❓ Why Other Options Are Incorrect

Option A) Hybridisation cannot occur before electrophoresis.
Option C) Blotting cannot occur before DNA isolation.
Option D) Hybridisation must occur after blotting.

🎯 Strategy

Used: Contextual/Tonal Matching

Option A → Wrong sequence.
Option B → Correct sequence.
Option C → Wrong sequence.
Option D → Hybridisation misplaced.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, DNA Fingerprinting.

15 The thermostable enzyme used in PCR is: (PYQ 2023 Shift 3)

A Taq polymerase

B Exonuclease

C RNA polymerase

D Endonuclease

💡 Short Explanation

Obtained from Thermus aquaticus. Remains active at high temperature. Essential for PCR.

✅ Correct Answer Explanation

PCR requires repeated heating cycles. Taq polymerase is thermostable and can withstand high temperatures used during DNA denaturation, making it ideal for PCR amplification.

❓ Why Other Options Are Incorrect

Option B) Removes nucleotides.
Option C) Synthesizes RNA.
Option D) Cuts DNA internally.

🎯 Strategy

Used: NCERT Recall

Option A → PCR enzyme.
Option B → DNA degradation.
Option C → Transcription.
Option D → Restriction function.

Final Answer → Taq polymerase.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, PCR.

16 Arrange the steps of 'Agarose gel electrophoresis' in the correct sequence: (PYQ 2023 Shift 3)
A. Cutting of bands of DNA from agarose gel
B. Visualisation of DNA fragments under UV radiation
C. Staining of DNA fragments with ethidium bromide
D. Movement of DNA fragments towards anode under electric field

A A, B, C, D

B D, C, B, A

C C, B, A, D

D B, D, C, A

💡 Short Explanation

DNA first migrates. Then stained. Visualized under UV. Desired band is cut.

✅ Correct Answer Explanation

Correct sequence: 1. DNA fragments move toward anode. 2. Gel is stained with ethidium bromide. 3. Bands are visualized under UV light. 4. Desired DNA bands are excised from gel.

❓ Why Other Options Are Incorrect

Option A) Cutting cannot occur first.
Option C) Staining occurs after electrophoresis.
Option D) Visualization cannot occur before electrophoresis.

🎯 Strategy

Used: Sequential Logic

Option A → Incorrect order.
Option B → Correct order.
Option C → Incorrect order.
Option D → Incorrect order.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Agarose Gel Electrophoresis.

17 Identify the correct statements regarding features of a vector: (PYQ 2023 Shift 3)
A. They should have ability to replicate within the host
B. They should have ‘ori’ sites that start replication
C. Its origin should not support high copy number
D. They should have more than one recognition sites for restriction enzyme

A C and D only

B A, B and C only

C A and B only

D B, C and D only

💡 Short Explanation

Vector must replicate. ori is essential. High copy number is desirable. Single unique restriction site preferred.

✅ Correct Answer Explanation

A cloning vector must: • Replicate inside the host. • Possess an origin of replication (ori). Statement C is incorrect because high copy number is generally desirable. Statement D is incorrect because vectors ideally contain unique restriction sites for cloning.

❓ Why Other Options Are Incorrect

Option A) Includes incorrect statements.
Option B) Includes statement C.
Option D) Includes C and D.

🎯 Strategy

Used: Elimination

Option A → Incorrect.
Option B → C incorrect.
Option C → Correct.
Option D → C and D incorrect.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Cloning Vectors.

18 Which technique is used to insert recombinant DNA into the nucleus of an animal cell? (PYQ 2023 Shift 3)

A Gene gun

B Insertion push

C Ligation

D Microinjection

💡 Short Explanation

DNA directly injected. Uses fine glass needle. Common in animal cells.

✅ Correct Answer Explanation

Microinjection involves directly injecting recombinant DNA into the nucleus of an animal cell using a fine microscopic needle. It is widely used in transgenic animal production.

❓ Why Other Options Are Incorrect

Option A) Mainly used for plant transformation.
Option B) Not a recognized biotechnology technique.
Option C) Joins DNA fragments.

🎯 Strategy

Used: NCERT Recall

Option A → Plant method.
Option B → Invalid technique.
Option C → DNA joining.
Option D → Correct.

Final Answer → Microinjection.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Gene Transfer Methods.

19 Observe the figures and answer the following questions.
SIMPLE STIRRED-TANK BIOREACTOR
Motor
│
│
Drive Shaft
│
│
Impeller
│
│ │
│ Culture │
│ Medium │
│ │
│ │
│
│
Air Inlet
SPARGED STIRRED-TANK BIOREACTOR
Motor
│
│
Drive Shaft
│
Impeller
│
│ │
│ Culture Medium │
│ │
│ ↑ ↑ ↑ ↑ ↑ ↑ │
│ Sparger Ring │
│ │
│ │
Air Inlet Sampling Port
Control Systems:
• Temperature Probe
• pH Probe
• Dissolved Oxygen Probe
• Foam Control
The parameters for optimal growth condition of living cells in bioreactor involve: (PYQ 2023 Shift 3)

A Temperature, Acids and Oxygen

B Temperature, Vitamins, Salts

C Temperature, pH, Vitamins, Oxygen, Salts

D pH, Oxygen, Salts

💡 Short Explanation

Bioreactors require controlled conditions. Growth depends on multiple parameters. Temperature, pH, oxygen and nutrients are essential.

✅ Correct Answer Explanation

For optimum growth and product formation, bioreactors maintain controlled environmental conditions including temperature, pH, dissolved oxygen, vitamins and mineral salts. These factors ensure maximum microbial or cellular activity.

❓ Why Other Options Are Incorrect

Option A) Incomplete; excludes pH, vitamins and salts.
Option B) Does not include oxygen and pH.
Option D) Omits temperature and vitamins.

🎯 Strategy

Used: Elimination

Option A → Incomplete.
Option B → Missing essential factors.
Option C → Complete set.
Option D → Incomplete.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Bioreactors.

20 Observe the figures and answer the following questions.
A
│
│ C │ ← └─────────┘
│
Shaft
│
│ │
│ │
│ G │
│
│
│ │
│ │
│ │
│ │
D E
Match the following: (PYQ 2023 Shift 3)

List I	List II
A. Foam Breaker	I. D
B. Sterile Air	II. C
C. Steam for sterilisation	III. E
D. Flat bladed impeller	IV. G

A A-I, B-II, C-IV, D-III

B A-II, B-III, C-I, D-IV

C A-III, B-I, C-IV, D-II

D A-II, B-IV, C-I, D-III

💡 Short Explanation

Foam breaker controls foam. Sterile air supplies oxygen. Steam sterilizes reactor. Impeller ensures mixing.

✅ Correct Answer Explanation

Based on the standard NCERT stirred-tank bioreactor diagram: • Foam breaker → C • Sterile air → E • Steam for sterilisation → D • Flat bladed impeller → G Thus the correct matching is Option B.

❓ Why Other Options Are Incorrect

Option A) Foam breaker and sterile air incorrectly matched.
Option C) Multiple mismatches.
Option D) Steam and impeller incorrectly matched.

🎯 Strategy

Used: Diagram Identification

Option A → Incorrect.
Option B → Correct.
Option C → Incorrect.
Option D → Incorrect.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Stirred Tank Bioreactor.

21 Observe the figures and answer the following questions.
What is the use of sampling ports? (PYQ 2023 Shift 3)
Foam Breaker
│
▼
│ │
Motor ─ Shaft ─┤ Culture │
│ Medium │
│ │
│ Impeller │
│ │
▲ ▲
│ │
Sterile Air Sampling
Inlet Port
│
▼
Small Sample Removal

A To withdraw large volumes of culture periodically

B To add large volumes of raw culture periodically

C To add large volume of raw culture in the beginning

D To withdraw small volumes of the culture periodically

💡 Short Explanation

Sampling ports monitor culture growth. Small quantities are removed. Helps quality control.

✅ Correct Answer Explanation

Sampling ports are used to periodically withdraw small samples from the bioreactor without contaminating the culture. These samples are analyzed to monitor growth and product formation.

❓ Why Other Options Are Incorrect

Option A) Large-scale withdrawal is not their purpose.
Option B) Used for sampling, not addition.
Option C) Culture is not introduced through sampling ports.

🎯 Strategy

Used: NCERT Recall

Option A → Incorrect.
Option B → Incorrect.
Option C → Incorrect.
Option D → Correct.

Final Answer → Option D.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Bioreactor Components.

22 Observe the figures and answer the following questions.
FIGURE II
│ │
│ │
│ ↑ ○ │
│ ○ ○ ○ │
│ ○ ○ ○ ○ │
│ ○ ○ ○ ○ ○ │
│ │
│ Sparger │
│
│
Air Inlet
What is the role of bubbles as shown in figure II? (PYQ 2023 Shift 3)

A To increase the oxygen transfer area

B To decrease the oxygen transfer area

C To increase the solubility of other gases

D To increase the solubility of salts

💡 Short Explanation

Air bubbles provide oxygen. Increase contact area. Improve aeration efficiency.

✅ Correct Answer Explanation

Bubbles generated in a bioreactor increase the surface area available for oxygen transfer between air and the culture medium. This enhances oxygen availability for growing cells.

❓ Why Other Options Are Incorrect

Option B) Opposite effect.
Option C) Not the primary purpose.
Option D) Unrelated to aeration.

🎯 Strategy

Used: Functional Analysis

Option A → Correct.
Option B → Opposite.
Option C → Secondary effect.
Option D → Unrelated.

Final Answer → Option A.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Aeration in Bioreactors.

23 Observe the figures and answer the following questions.
FIGURE I
Simple Stirred-Tank Bioreactor
Motor
│
│
Drive Shaft
│
Impeller
│
│ │
│ Culture │
│ Medium │
│ │
Curved Base
FIGURE II
Sparged Stirred-Tank Bioreactor
Motor
│
│
Drive Shaft
│
Impeller
│
│ │
│ ○ ○ ○ ○ │
│ ○ ○ ○ ○ ○ │
│ │
Sparger
│
Sterile Air
Curved Base
Identify the statements which are correct with respect to the above figures I and II. (PYQ 2023 Shift 3)
(A) I represent increased surface area for oxygen transfer
(B) Fig II is of simple stirred-tank bioreactor
(C) A stirred-tank reactor is usually cylindrical with a curved base
(D) The base of the tank is curved to facilitate mixing of the reactor contents

A A and D only

B B and C only

C C and D only

D B and D only

💡 Short Explanation

Stirred tank reactors are cylindrical. Curved base improves mixing. Figure I does not represent oxygen transfer area.

✅ Correct Answer Explanation

NCERT describes stirred-tank bioreactors as cylindrical vessels with a curved base that facilitates efficient mixing of the reactor contents. Therefore, statements C and D are correct.

❓ Why Other Options Are Incorrect

Option A) Statement A is incorrect.
Option B) Statement B is not correct for the figure.
Option D) Includes incorrect statement B.

🎯 Strategy

Used: Elimination

Option A → A incorrect.
Option B → B incorrect.
Option C → Correct pair.
Option D → B incorrect.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII, Biology, Biotechnology Principles and Processes, Bioreactors.

24 A thermostable DNA polymerase is isolated from: (PYQ 2024 Shift 1, 2024 Shift 2)

A Thermus aquaticus

B Agrobacterium tumefaciens

C E. coli

D Salmonella typhimurium

💡 Short Explanation

Source of Taq polymerase. Survives high temperatures. Essential for PCR.

✅ Correct Answer Explanation

Thermus aquaticus is a thermophilic bacterium found in hot springs. Taq polymerase isolated from it remains active at high temperatures used during PCR denaturation cycles.

❓ Why Other Options Are Incorrect

Option B) Causes crown gall disease; not source of Taq polymerase.
Option C) Common laboratory bacterium but lacks thermostable polymerase.
Option D) Pathogenic bacterium; not used for thermostable polymerase.

🎯 Strategy

Used: Elimination

Option A → Known source of Taq polymerase.
Option B → Plant pathogen.
Option C → Non-thermophilic.
Option D → Non-thermophilic.

Final Answer → Option A.

🧠 Memory Trick

📚 Class XII Biology, Chapter 11: Biotechnology Principles and Processes, PCR.

25 Which one of the following is not a process of DNA recombinant technology? (PYQ 2024 Shift 1, 2024 Shift 2)

A Isolation of DNA

B RNA interference (RNAi)

C Introduction of Restriction endonucleases

D Culturing the host cells in a medium at a large scale

💡 Short Explanation

RNAi is gene silencing. Not a core rDNA step. Used in pest resistance.

✅ Correct Answer Explanation

RNA interference is a biological mechanism that silences gene expression using dsRNA. It is not one of the standard steps of recombinant DNA technology.

❓ Why Other Options Are Incorrect

Option A) Essential first step.
Option C) Required for DNA cutting.
Option D) Required for large-scale product production.

🎯 Strategy

Used: Odd One Out

Option A → rDNA process.
Option B → Gene silencing mechanism.
Option C → rDNA process.
Option D → rDNA process.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII Biology, Chapters 11 & 12.

26 Arrange the following steps of DNA fingerprinting in proper sequence: (PYQ 2024 Shift 1, 2024 Shift 2)
(A) Hybridisation using labelled VNTR probe
(B) Separation of DNA fragments by electrophoresis
(C) Digestion of DNA by restriction endonucleases
(D) Blotting of separated DNA fragments to nylon
(E) Isolation of DNA

A (C), (A), (B), (D), (E)

B (E), (C), (B), (D), (A)

C (B), (C), (D), (E), (A)

D (C), (D), (B), (A), (E)

💡 Short Explanation

DNA isolated first. Digested and separated. Hybridisation occurs last.

✅ Correct Answer Explanation

The correct sequence is: Isolation of DNA → Restriction digestion → Electrophoresis → Southern blotting → Hybridisation with VNTR probe. Thus: (E) → (C) → (B) → (D) → (A)

❓ Why Other Options Are Incorrect

Option A) Starts with digestion before DNA isolation.
Option C) Electrophoresis cannot occur before digestion.
Option D) Blotting cannot precede electrophoresis.

🎯 Strategy

Used: Option Grouping

Option A → Sequence incorrect.
Option B → Matches standard DNA fingerprinting steps.
Option C → Wrong order.
Option D → Wrong order.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII Biology, DNA Fingerprinting.

27 Which of the following statements is not correct for Restriction enzymes? (PYQ 2024 Shift 1, 2024 Shift 2)

A Exonucleases remove nucleotide from ends of the DNA.

B Endonucleases make cuts at specific positions within the DNA.

C Ligases join sticky ends of DNA together.

D The first restriction endonuclease was Hind II.

💡 Short Explanation

Ligase is not a restriction enzyme. Restriction enzymes cut DNA. Ligases join DNA fragments.

✅ Correct Answer Explanation

Restriction enzymes are nucleases that cut DNA. DNA ligase is a separate enzyme used to join DNA fragments together. Therefore, option C is not correct regarding restriction enzymes.

❓ Why Other Options Are Incorrect

Option A) Correct function of exonucleases.
Option B) Correct function of endonucleases.
Option D) Hind II was the first restriction endonuclease isolated.

🎯 Strategy

Used: Odd One Out

Option A → Restriction enzyme concept.
Option B → Restriction enzyme concept.
Option C → Different enzyme.
Option D → Historical fact.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII Biology, Biotechnology Principles and Processes.

28 Given below are two statements: (PYQ 2024 Shift 1)
Statement I: In a bioreactor, small volume of cultures are developed in which useful bio-products are produced.
Statement II: In downstream processing, the products formulated with suitable preservatives are ready for marketing without testing of their quality.

A Both Statement I and Statement II are true

B Both Statement I and Statement II are false

C Statement I is true, but Statement II is false

D Statement I is false, but Statement II is true

💡 Short Explanation

Bioreactors use large volumes. Quality testing is mandatory. Both statements are incorrect.

✅ Correct Answer Explanation

Bioreactors are large vessels designed for large-scale production of bio-products. During downstream processing, products must undergo quality control and testing before marketing.

❓ Why Other Options Are Incorrect

Option A) Both statements are false.
Option C) Statement I is false.
Option D) Statement II is false.

🎯 Strategy

Used: Elimination

Option A → Incorrect.
Option B → Both false.
Option C → Statement I false.
Option D → Statement II false.

Final Answer → Option B.

🧠 Memory Trick

📚 Class XII Biology, Biotechnology Principles and Processes.

29 Arrange the given steps involved in gel electrophoresis used for separation of DNA fragments: (PYQ 2025 Shift 1)
(A) Exposure to UV light
(B) Staining with ethidium bromide
(C) Moving of DNA fragments towards anode
(D) Elution

A (A), (B), (C), (D)

B (B), (A), (D), (C)

C (A), (D), (B), (C)

D (C), (B), (A), (D)

💡 Short Explanation

DNA first migrates in gel. DNA bands are stained. Bands are visualized under UV. Desired fragments are eluted.

✅ Correct Answer Explanation

In gel electrophoresis, negatively charged DNA fragments first move towards the positive electrode (anode). After separation, the gel is stained with ethidium bromide to make DNA visible. The stained bands are then viewed under ultraviolet light. Finally, the desired DNA fragment is cut out and purified through elution.

❓ Why Other Options Are Incorrect

Option A) UV visualization cannot occur before staining and electrophoresis.
Option B) DNA movement must occur before staining and visualization.
Option C) Elution takes place only after DNA visualization.

🎯 Strategy

Used: Sequential Biology Process

Option A → Incorrect order.
Option B → DNA migration placed incorrectly.
Option C → Elution too early.
Option D → Correct sequence.

Final Answer → Option D.

🧠 Memory Trick

📚 Class XII Biology, Chapter 11 – Biotechnology: Principles and Processes, Gel Electrophoresis.

30 EcoRI, a significant tool in rDNA technology is: (PYQ 2025 Shift 1)

A Bacteria

B Plasmid

C Enzyme

D Purine

💡 Short Explanation

EcoRI is a restriction endonuclease. It cuts DNA at specific sequences. Essential in recombinant DNA technology.

✅ Correct Answer Explanation

EcoRI is a restriction endonuclease isolated from Escherichia coli. It recognizes the palindromic sequence GAATTC and cuts DNA at specific positions, generating sticky ends. These sticky ends facilitate insertion of foreign DNA into vectors.

❓ Why Other Options Are Incorrect

Option A) EcoRI is obtained from bacteria but is not itself a bacterium.
Option B) A plasmid is a circular DNA molecule; EcoRI is not a plasmid.
Option D) Purines are nitrogenous bases, not restriction enzymes.

🎯 Strategy

Used: NCERT Recall

Option A → Source organism.
Option B → DNA vector.
Option C → Restriction enzyme.

Final Answer → Option C.

🧠 Memory Trick

📚 Class XII Biology, Chapter 11 – Biotechnology: Principles and Processes, Restriction Endonucleases.

31 Which of the following steps are related to Polymerase Chain Reaction (PCR)? (PYQ 2025 Shift 1)
(A) Extension
(B) Annealing
(C) Propagation
(D) Denaturation

A (A), (B) and (D) only

B (A), (B) and (C) only

C (A), (B), (C) and (D)

D (B), (C) and (D) only

💡 Short Explanation

PCR has three major steps. Denaturation separates strands. Annealing and extension complete amplification.

✅ Correct Answer Explanation

PCR involves three cyclic steps: 1. Denaturation – DNA strands separate. 2. Annealing – Primers bind to complementary sequences. 3. Extension – Taq polymerase synthesizes new DNA strands. Propagation is not a standard PCR step.

❓ Why Other Options Are Incorrect

Option B) Includes propagation and excludes denaturation.
Option C) Propagation is not a PCR step.
Option D) Excludes extension, which is essential.

🎯 Strategy

Used: NCERT Recall

Option A → Contains all three PCR stages.
Option B → Missing denaturation.
Option C → Includes non-PCR term.
Option D → Missing extension.

Final Answer → Option A.

🧠 Memory Trick

📚 Class XII Biology, Chapter 11 – Biotechnology: Principles and Processes, PCR.

CUET UG Categorised PYQ Biology Unit 9

Test Complete!

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