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Class 12 · Biology · Chapter 9

Biotechnology: Principles and Processes: Class 12 Important Questions with Answers

72 important questions for Class 12 Biology Chapter 9, Biotechnology: Principles and Processes, the way they come in the board exam: MCQs, assertion–reason, case-based and short and long answer questions, with answers. Taken from our Class 12 Biology notes for 2026-27.

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Jump to: Practice set: test yourself20 MCQsAssertion–ReasonAnswers to the practice set

Practice set: test yourself

Try every question before looking at the answers below. 64 or more out of 80 means you are ready for the board.

A. Fill in the blanks (1 mark each)

  1. The first recombinant DNA was made by Cohen and ______.
  2. The first restriction enzyme isolated was ______.
  3. The R in EcoRI stands for strain ______.
  4. DNA moves towards the ______ in electrophoresis.
  5. Extraction of DNA from gel is called ______.
  6. The gene rop in pBR322 codes for proteins of ______.
  7. Taq polymerase comes from ______.
  8. The plant vector is the ______ plasmid.

B. True or false? (1 mark each)

  1. Exonucleases cut within DNA.
  2. Agarose is obtained from seaweeds.
  3. Smaller DNA fragments move farther.
  4. Recombinant colonies are blue on X-gal.
  5. Chitinase breaks plant cell walls.
  6. Agrobacterium infects dicots.
  7. DNA can easily pass through cell membranes.
  8. Sparged bioreactors bubble sterile air.

C. Very short answer (1 mark each)

  1. Write the EcoRI recognition sequence.
  2. Name two selectable markers in pBR322.
  3. Name the sites in tetR.
  4. Which chemical precipitates DNA?
  5. Name the three steps of PCR.
  6. What is a recombinant protein?
  7. Name the enzyme used to break bacterial cells.
  8. Why is ethidium bromide used?
  9. Expand PCR.
  10. What is a palindrome?

D. Short answer I (2 marks each)

  1. Explain the naming of EcoRI.
  2. What are sticky ends? Why are they useful?
  3. Give two features of a good cloning vector.
  4. How are bacteria made competent?
  5. Explain insertional inactivation.
  6. Distinguish microinjection and biolistics.
  7. Why is Taq polymerase used in PCR?
  8. What is downstream processing?
My score (fill in after checking the answers)
SectionA /8B /8C /10D /16E /18F /20G (bonus)Total /80
My marks

Rough work

E. Short answer II (3 marks each)

  1. Describe the principle and steps of gel electrophoresis.
  2. Describe the role of ori, selectable marker and cloning site.
  3. Explain how Agrobacterium is used as a vector.
  4. Describe the isolation of DNA.
  5. Explain one cycle of PCR.
  6. Describe a stirred-tank bioreactor.

F. Long answer (5 marks each)

  1. Describe the steps of recombinant DNA technology from isolation of DNA to obtaining the product.
  2. Describe pBR322 with a diagram and explain how recombinants are selected.

G. HOTS (higher-order thinking)

  1. Why must vector and source DNA be cut by the same enzyme?
  2. Why are restriction enzymes not harmful to bacteria themselves?
  3. Why is a single recognition site per enzyme preferred in a vector?
  4. Why do bands not appear in a gel run with reversed electrodes?

20 MCQs

  1. Molecular scissors are
    (a) ligases (b) polymerases (c) restriction enzymes (d) lysozymes
  2. EcoRI cuts between
    (a) G and A (b) A and T (c) C and G (d) T and C
  3. Hind II recognises a sequence of
    (a) 4 bp (b) 2 bp (c) 8 bp (d) 6 bp
  4. DNA in a gel is seen with
    (a) iodine (b) ethidium bromide under UV (c) safranin (d) visible light only
  5. Agarose acts as
    (a) stain (b) sieve (c) enzyme (d) vector
  6. The ori controls
    (a) selection (b) expression only (c) cutting (d) copy number
  7. BamHI site in pBR322 is in
    (a) tetR (b) ampR (c) rop (d) ori
  8. Recombinants on X-gal are
    (a) blue (b) red (c) colourless (d) green
  9. Agrobacterium transfers
    (a) Ti plasmid fully (b) protein (c) RNA (d) T-DNA
  10. Competence is induced by
    (a) Na⁺ (b) Ca²⁺ (c) K⁺ (d) Cl⁻
  11. Heat shock temperature
    (a) 94 °C (b) 4 °C (c) 42 °C (d) 72 °C
  12. Gene gun uses particles of
    (a) gold or tungsten (b) iron (c) silver (d) copper
  13. Fungal cell walls are broken by
    (a) cellulase (b) chitinase (c) lysozyme (d) protease
  14. DNA is precipitated by
    (a) warm water (b) acid (c) chilled ethanol (d) salt only
  15. In PCR primers bind during
    (a) denaturation (b) ligation (c) extension (d) annealing
  16. Taq polymerase is from
    (a) Thermus aquaticus (b) E. coli (c) Bacillus (d) yeast
  17. After 30 PCR cycles, copies ≈
    (a) 1 billion (b) 1 million (c) 1 thousand (d) 30
  18. Most common bioreactor
    (a) shake flask (b) Petri dish (c) column (d) stirred-tank
  19. Purification of the product is
    (a) upstream (b) downstream processing (c) cloning (d) ligation
  20. First rDNA used a plasmid of
    (a) E. coli (b) Agrobacterium (c) Salmonella typhimurium (d) Bacillus

1 (c) · 2 (a) · 3 (d) · 4 (b) · 5 (b) · 6 (d) · 7 (a) · 8 (c) · 9 (d) · 10 (b) · 11 (c) · 12 (a) · 13 (b) · 14 (c) · 15 (d) · 16 (a) · 17 (a) · 18 (d) · 19 (b) · 20 (c)

Assertion–Reason (6)

(a) Both true, R explains A. (b) Both true, R does not explain A. (c) A true, R false. (d) A false, R true.

  1. A: DNA fragments separate in agarose gel. R: Agarose gives a sieving effect by size.
  2. A: The same enzyme cuts vector and alien DNA. R: It produces complementary sticky ends.
  3. A: Bacteria take up DNA easily. R: DNA is hydrophilic.
  4. A: Taq polymerase is used in PCR. R: It remains active at high temperature.
  5. A: Insertion at BamHI makes the plasmid lose ampicillin resistance. R: BamHI lies in tetR.
  6. A: Agrobacterium is used for monocots. R: It delivers T-DNA into plant cells.

Key: 1 (a) · 2 (a) · 3 (d) · 4 (a) · 5 (d) · 6 (d)

Answers to the practice set

A. 1. Boyer 2. Hind II 3. RY13 4. anode 5. elution 6. plasmid replication 7. Thermus aquaticus 8. Ti

B. 1. F 2. T 3. T 4. F (colourless) 5. F (fungal) 6. T 7. F 8. T

C. 1. 5′-GAATTC-3′ / 3′-CTTAAG-5′ 2. ampR, tetR 3. BamHI, SalI 4. chilled ethanol 5. denaturation, annealing, extension 6. a protein encoded by a foreign gene expressed in a host 7. lysozyme 8. to stain DNA so that bands are seen under UV 9. polymerase chain reaction 10. a sequence that reads the same on the two strands in the 5′→3′ direction

D. 1. E: Escherichia, co: coli, R: strain RY13, I: first enzyme isolated from it 2. Single-stranded overhangs left after cutting; they H-bond with complementary ends so ligase can join vector and insert 3. Any two: ori, selectable marker, single cloning sites, small size 4. Ca²⁺ treatment, incubation with rDNA on ice, heat shock at 42 °C, back to ice 5. Insertion of foreign DNA into a marker gene (e.g. lacZ) inactivates it; recombinants are identified because they lose that function (colourless colonies) 6. Microinjection: rDNA injected into the nucleus of an animal cell; biolistics: plant cells bombarded with DNA-coated gold or tungsten particles 7. It is thermostable and survives the high temperature of denaturation 8. Separation and purification of the product, formulation, clinical trials and quality control

Answers to E, F, G, case study (short, long and HOTS answers, step by step) are in the notes pack

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