Question Bank — Biotechnology: Principles and Processes

NCERT Class 12 Biology · Chapter 9 · CBSE Board Pattern

Class 12 Biology Chapter 9 Question Bank CBSE Board Pattern

Section A — MCQs (10 questions, 1 mark each)

1. Which of the following is the definition of biotechnology given by the European Federation of Biotechnology (EFB)?
(a) Integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services
(b) Use of microbes to produce curd and wine only
(c) Production of test-tube babies
(d) Synthesis of genes for DNA vaccines

2. The first recombinant DNA was constructed by linking an antibiotic resistance gene with the plasmid of:
(a) Escherichia coli
(b) Salmonella typhimurium
(c) Thermus aquaticus
(d) Agrobacterium tumefaciens

3. Restriction endonucleases cut DNA at specific palindromic sequences. The enzyme EcoRI recognises the sequence:
(a) 5′-GAATTC-3′
(b) 5′-AAGCTT-3′
(c) 5′-GGATCC-3′
(d) 5′-GATATC-3′

4. In pBR322, insertion of foreign DNA at the BamHI site of the tetracycline resistance gene results in:
(a) Loss of tetracycline resistance but retention of ampicillin resistance
(b) Loss of both resistances
(c) Gain of kanamycin resistance
(d) No change in resistance

5. The process of making bacterial cells competent to take up recombinant DNA by treating them with calcium ions followed by heat shock is called:
(a) Transformation
(b) Transduction
(c) Conjugation
(d) Electroporation

6. PCR utilises a thermostable DNA polymerase isolated from:
(a) Escherichia coli
(b) Thermus aquaticus
(c) Salmonella typhimurium
(d) Agrobacterium tumefaciens

7. Assertion (A): Origin of replication (ori) is essential for a cloning vector.
Reason (R): ori sequence controls the copy number of the linked DNA and initiates replication.
(1) Both A and R are true and R is the correct explanation of A.
(2) Both A and R are true but R is not the correct explanation of A.
(3) A is true but R is false.
(4) A is false but R is true.

8. Assertion (A): Insertional inactivation of the lacZ gene allows selection of recombinants on the basis of colour.
Reason (R): Presence of insert within the β-galactosidase gene prevents production of the enzyme, resulting in white colonies.
(1) Both A and R are true and R is the correct explanation of A.
(2) Both A and R are true but R is not the correct explanation of A.
(3) A is true but R is false.
(4) A is false but R is true.

9. Which technique separates DNA fragments according to size using a negatively charged agarose matrix under an electric field?
(a) PCR
(b) Gel electrophoresis
(c) Downstream processing
(d) Biolistics

10. The stirred-tank bioreactor provides optimum conditions for microbial growth by controlling all of the following except:
(a) Temperature and pH
(b) Foam and oxygen supply
(c) Agitation for even mixing
(d) Introduction of restriction enzymes

Section B — Very Short Answer (6 questions, 2 marks each)

11. Differentiate between exonucleases and endonucleases.
12. What is the role of DNA ligase in the formation of recombinant DNA?
13. Name the two core techniques that enabled the birth of modern biotechnology.
14. Why is chilled ethanol used during isolation of DNA?
15. State two features of a good cloning vector besides the origin of replication.
16. What is insertional inactivation? How does it help in selection of recombinants?

Section C — Short Answer (5 questions, 3 marks each)

17. Explain the three basic steps involved in genetically modifying an organism.
18. Describe how Agrobacterium tumefaciens has been modified to act as a vector for gene transfer in plants.
19. What is gel electrophoresis? How are DNA fragments visualised after separation?
20. Differentiate between selectable marker and reporter gene with suitable examples from pBR322 and lacZ.
21. Write any three advantages of stirred-tank bioreactors over shake flasks.

Section D — Long Answer (3 questions, 5 marks each)

22. Describe the process of Polymerase Chain Reaction (PCR) with the help of a labelled diagram showing the three steps in each cycle. (Diagram description required)
23. Explain the features of an ideal cloning vector with special reference to pBR322. How do antibiotic resistance genes help in selection of recombinants?
24. Describe the various steps involved in the isolation of genetic material (DNA) from bacterial, plant or fungal cells. Why must DNA be free from other macromolecules before restriction digestion?

Section E — Case/Source-Based (2 questions, 4 marks each)

25. Case: A researcher isolates a gene of interest from human DNA, cuts both the gene and a bacterial plasmid with EcoRI, ligates them using DNA ligase and introduces the recombinant plasmid into competent E. coli cells. The cells are then grown on ampicillin-containing medium.
(a) Name the enzyme that cuts DNA at specific palindromic sequences. (1)
(b) Why do the cut ends of the vector and insert have “sticky ends”? (1)
(c) What is the role of the ampicillin resistance gene in this experiment? (1)
(d) Name the process by which the recombinant DNA is forced into competent bacterial cells. (1)

26. Case: A biotechnology company uses a stirred-tank bioreactor of 500-litre capacity to produce a recombinant protein. After the biosynthetic phase, the product is subjected to separation, purification and formulation.
(a) What is the function of the agitator system and oxygen delivery system in the bioreactor? (1)
(b) Define downstream processing. (1)
(c) Why is large-scale production in bioreactors preferred over small-volume cultures? (1)
(d) Name the two most commonly used methods for introducing alien DNA into plant and animal cells besides chemical treatment. (1)

▶ Answer Key Attempt all questions first,
then tap to reveal

Section A

  1. (a)
  2. (b)
  3. (a)
  4. (a)
  5. (a)
  6. (b)
  7. (1)
  8. (1)
  9. (b)
  10. (d)

Section B

  1. Exonucleases remove nucleotides from ends; endonucleases cut at specific internal positions (1+1).
  2. Joins cut ends of DNA fragments by forming phosphodiester bonds (2).
  3. Genetic engineering and bioprocess engineering (1+1).
  4. DNA precipitates as fine threads (2).
  5. Selectable marker and cloning site (1+1).
  6. Insertion of foreign DNA into lacZ gene inactivates β-galactosidase; recombinants give white colonies (2).

Section C

  1. Identification of desirable DNA, introduction into host, maintenance and transfer to progeny (1 each).
  2. Ti plasmid modified to non-pathogenic form; T-DNA used to deliver genes of interest (3).
  3. Negatively charged DNA moves to anode through agarose; smaller fragments move farther; visualised by ethidium bromide + UV (3).
  4. Antibiotic resistance genes select transformants; lacZ allows blue-white screening via insertional inactivation (3).
  5. Better control of pH, temperature, foam; sampling ports; higher biomass (any three).

Section D

  1. Denaturation (94°C), primer annealing (50–65°C), extension (72°C) by Taq polymerase; diagram labels: template, primers, dNTPs, Taq polymerase, cycles (5).
  2. ori, selectable marker (ampR, tetR), cloning sites, insertional inactivation; plating on two antibiotics distinguishes recombinants (5).
  3. Cell lysis (lysozyme/cellulase/chitinase), removal of RNA/proteins, precipitation with chilled ethanol; purity required for specific cutting by restriction enzymes (5).

Section E

  1. (a) Restriction endonuclease (1)
    (b) Cuts away from centre of palindrome leave single-stranded overhangs (1)
    (c) Selects only transformed cells (1)
    (d) Transformation / heat shock (1)

  2. (a) Ensures uniform mixing and oxygen supply (1)
    (b) Separation, purification and formulation of product (1)
    (c) Small volumes give low yield; large biomass needed for commercial production (1)
    (d) Biolistics / microinjection / disarmed pathogen vectors (any two) (1)

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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.