Section 13 — Board Exam-Pattern Questions (Class 12 Biology · Chapter 10)
Chapter 10 (Biotechnology and Its Applications) is one of the most dependable scoring chapters in the Class 12 Biology Board paper. As a broad guide, about 5-8 marks of a typical paper tend to come from this chapter — spread across MCQs, 2/3-mark short answers, and very often a 5-mark question on GM crops, insulin, gene therapy or transgenic animals.
This section curates 24 high-yield Board questions in the format and weighting examiners typically use:
| Marks | Number of Qs | Typical paper allocation |
|---|---|---|
| 1 mark | 7 questions (Q1-Q7) | 2-3 / paper |
| 2 marks | 6 questions (Q8-Q13) | 2 / paper |
| 3 marks | 6 questions (Q14-Q19) | 1-2 / paper |
| 5 marks | 5 questions (Q20-Q24) | 1 / paper (very high probability) |
| Total | 24 questions | ~24 marks worth |
How to use: Cover the answer, attempt it yourself scaled to the marks, then check against the model answer and its keyword notes.
No quiz at the end: Pair this set with the Solved Examples section.
What the Examiners Keep Asking
Most questions on Chapter 10 fall into six recurring themes:
1. Plant tissue culture (1- or 2-mark) — totipotency, explant, micropropagation, somaclones, virus-free plants, somatic hybridisation and the pomato.
2. GM crops (2-, 3- or 5-mark) — meaning of a GMO, benefits, golden rice, and tailor-made industrial plants.
3. Bt crops and RNAi (2-, 3- or 5-mark) — Bacillus thuringiensis, protoxin activation, cry genes, and the RNA-interference strategy against the tobacco nematode.
4. Biotechnology in medicine (3- or 5-mark) — recombinant insulin and the Eli Lilly method, the C peptide, and gene therapy for ADA deficiency.
5. Molecular diagnosis (2- or 3-mark) — PCR, radioactive probes with autoradiography, and ELISA.
6. Transgenic animals and ethics (3- or 5-mark) — uses of transgenic animals, Rosie, GEAC, patents and biopiracy.
1-Mark Questions (Q1-Q7)
Q1. [1 mark] Define totipotency.
Answer: The capacity of a single cell or explant to generate a whole plant.
Keyword note: the idea of a whole plant from one cell carries the mark.
Q2. [1 mark] What is the full form of GEAC?
Answer: Genetic Engineering Approval Committee.
Q3. [1 mark] Name the bacterium that produces the Bt toxin.
Answer: Bacillus thuringiensis.
Q4. [1 mark · Assertion-Reason]
Assertion (A): The Bt protoxin does not harm the Bacillus that produces it. Reason (R): The protoxin is converted into the active toxin only in the alkaline pH of the insect gut.
Options: (a) Both A and R true and R explains A. (b) Both true but R doesn't explain A. (c) A true, R false. (d) A false, R true.
Answer: (a) — the toxin is stored as an inactive protoxin, and because activation needs the alkaline insect gut, it stays harmless inside the bacterium, so R correctly explains A.
Q5. [1 mark] What is a somaclone?
Answer: A plant produced by micropropagation that is genetically identical to the parent plant from which it was grown.
Q6. [1 mark] Name the type of vector used to introduce the functional ADA gene into the patient's lymphocytes.
Answer: A retroviral vector.
Q7. [1 mark] Golden rice is enriched with which vitamin?
Answer: Vitamin A.
2-Mark Questions (Q8-Q13)
Q8. [2 marks] What is micropropagation, and why are the plants it produces called somaclones?
Answer: Micropropagation is the method of producing thousands of plants through tissue culture in a short duration. The plants are called somaclones because each is genetically identical to the original plant from which it was raised.
Keyword note: both the definition and the reason for the name are needed.
Q9. [2 marks] What is somatic hybridisation? Name the somatic hybrid produced from tomato and potato.
Answer: Somatic hybridisation is the fusion of naked protoplasts from two different plant varieties to form a hybrid protoplast, which is grown into a somatic hybrid. Fusing tomato and potato protoplasts produced the pomato, though it lacked all the characters needed for commercial use.
Q10. [2 marks] Why can insulin not be taken orally, and what problem did animal-derived insulin cause?
Answer: Being a protein, insulin would be digested in the gut if swallowed, so it is injected. Insulin extracted from the pancreas of slaughtered cattle and pigs was a foreign animal protein and sometimes caused allergy or immune reactions in patients.
Q11. [2 marks] Define RNA interference and state the natural sources of the RNA that can trigger it.
Answer: RNA interference (RNAi) is a method of cellular defence in eukaryotes in which a complementary double-stranded RNA (dsRNA) silences a specific mRNA by preventing its translation. The triggering complementary RNA can come from viruses with RNA genomes or from transposons that replicate via an RNA intermediate.
Q12. [2 marks] State any two uses of transgenic animals, with an example of each.
Answer: (i) Study of disease — building models for human diseases such as cancer or Alzheimer's to test treatments. (ii) Biological products — producing useful proteins, e.g. the transgenic cow Rosie, whose milk carried human alpha-lactalbumin (2.4 g/litre). (Vaccine safety testing and toxicity testing are equally acceptable.)
Q13. [2 marks] How does PCR allow early detection of a pathogen, and give one clinical use.
Answer: PCR detects a very low concentration of a bacterium or virus by amplifying its nucleic acid into many copies, so it can be found before symptoms appear. It is used, for example, to detect HIV in suspected AIDS patients (also gene mutations in suspected cancer patients).
3-Mark Questions (Q14-Q19)
Q14. [3 marks] Explain the mode of action of the Bt toxin inside a target insect.
Answer: The bacterium stores the toxin as an inactive protoxin in protein crystals. When an insect ingests it, the alkaline pH of the gut solubilises the crystals and converts the protoxin into the active toxin. The toxin then binds the surface of the midgut epithelial cells, creates pores in their membranes, so the cells swell and burst (lysis), and the insect dies.
Keyword note: protoxin, alkaline gut activation, binds midgut cells, pores and lysis.
Q15. [3 marks] What are cry genes? Give the pests controlled by cryIAc/cryIIAb and by cryIAb, and name the insect groups Bt toxins target.
Answer: cry genes code for the insecticidal Bt (Cry) proteins. cryIAc and cryIIAb control the cotton bollworms, while cryIAb controls the corn borer. Different Bt toxins are specific to particular insect groups — lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
Q16. [3 marks] How did Eli Lilly produce human insulin using recombinant DNA technology? Mention the role of the C peptide.
Answer: In 1983 Eli Lilly prepared two DNA sequences for chain A and chain B of human insulin and introduced them into plasmids of E. coli, so the two chains were produced separately. The chains were then extracted and combined by creating disulphide bonds to form mature insulin. The C peptide, present in the natural pro-hormone, is removed during maturation and is absent from mature insulin, which is why the chains had to be assembled directly.
Q17. [3 marks] Describe the gene-therapy procedure used to treat ADA deficiency, and state its main limitation.
Answer: Lymphocytes are taken from the patient's blood and grown in culture; a functional ADA cDNA carried by a retroviral vector is introduced into them, and the corrected cells are returned to the patient, where they make the missing enzyme. The limitation is that these lymphocytes are not immortal, so the patient needs periodic infusions; a permanent cure would need the gene introduced at early embryonic stages.
Q18. [3 marks] Describe three techniques used for early molecular diagnosis of disease.
Answer: (1) PCR amplifies a pathogen's nucleic acid to detect very low concentrations, e.g. HIV or cancer-causing mutations. (2) A radioactively tagged single-stranded probe is allowed to hybridise with complementary DNA and read by autoradiography; a mutated gene gives no signal because the probe cannot pair with it. (3) ELISA works on antigen-antibody interaction, detecting either the pathogen's antigens or the antibodies made against it.
Q19. [3 marks] What is biopiracy? Explain it using the Basmati example and name the body that regulates GM work in India.
Answer: Biopiracy is the use of bio-resources without proper authorisation and without compensatory payment to the source country and people. In 1997 an American company patented Basmati rice, a 'new' variety actually derived from Indian farmers' varieties crossed with semi-dwarf ones (India has ~200,000 rice varieties and 27 documented Basmati types). GM research and release in India are regulated by the GEAC (Genetic Engineering Approval Committee).
5-Mark Questions (Q20-Q24)
Q20. [5 marks] What is a Genetically Modified Organism? Explain, with examples, how genetic modification has made crops more useful.
Answer:
A Genetically Modified Organism (GMO) is a plant, bacterium, fungus or animal whose genes have been altered by manipulation; in agriculture the focus is on GM plants.
Genetic modification has made crops more useful in several ways:
- Tolerance to abiotic stresses — cold, drought, salt and heat.
- Pest resistance — reducing reliance on chemical pesticides.
- Reduced post-harvest losses, so more of the crop reaches people.
- Efficient mineral use, which prevents early exhaustion of soil fertility.
- Enhanced nutrition — the flagship example being golden rice, enriched with vitamin A.
- Tailor-made plants that supply industry with starches, fuels and pharmaceuticals.
Keyword note: GMO definition plus the six benefit points, with golden rice named.
Q21. [5 marks] How were tobacco plants protected from the nematode Meloidogyne incognita? Explain RNA interference and the strategy step by step.
Answer:
The nematode Meloidogyne incognita infects the roots of tobacco and greatly reduces yield. It was countered using RNA interference (RNAi), a cellular defence present in all eukaryotes in which a complementary double-stranded RNA (dsRNA) silences a specific mRNA by preventing its translation.
The strategy: Agrobacterium vectors were used to introduce nematode-specific genes into the tobacco plant, arranged so that the host cells produced both sense and anti-sense RNA. Being complementary, these two strands paired to form a dsRNA, which triggered RNAi and silenced the specific mRNA of the nematode — a gene the parasite needed to survive.
As a result, the nematode could not survive in the transgenic host expressing the interfering RNA, so the plant was protected without any pesticide. In nature the triggering RNA can come from RNA viruses or transposons.
Q22. [5 marks] Describe the production of human insulin by recombinant DNA technology. Include its structure, the pro-hormone, the earlier source and the Eli Lilly method.
Answer:
Structure: insulin has two short polypeptide chains, A and B, linked by disulphide bridges.
Pro-hormone: in mammals it is first made as a pro-hormone carrying an extra C peptide, which is removed during maturation and is absent from mature insulin.
Earlier source and its problem: before biotechnology, insulin was extracted from the pancreas of slaughtered cattle and pigs; this animal insulin sometimes caused allergy or immune reactions, and being a protein it cannot be taken orally as it would be digested.
The Eli Lilly method (1983): the main challenge was assembling insulin into its mature two-chain form. Eli Lilly prepared two DNA sequences for chains A and B, introduced them into plasmids of E. coli to produce the chains separately, then extracted and combined them by creating disulphide bonds to form human insulin — a molecule identical to the natural hormone and free of animal-source immune problems.
Q23. [5 marks] What is a transgenic animal? Describe any five uses of transgenic animals with examples.
Answer:
A transgenic animal is one whose DNA has been manipulated so that it possesses and expresses an extra (foreign) gene; over 95 per cent are mice.
Their five main uses:
- Normal physiology and development — studying how genes are regulated, e.g. the role of insulin-like growth factor.
- Study of disease — models for cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's to test new treatments.
- Biological products — making costly proteins cheaply, e.g. alpha-1-antitrypsin for emphysema; the transgenic cow Rosie (1997) gave milk with human alpha-lactalbumin at 2.4 g/litre.
- Vaccine safety testing — transgenic mice test the polio vaccine, possibly replacing monkeys.
- Chemical (toxicity) safety testing — animals made more sensitive to toxins give results in less time.
Q24. [5 marks] What is gene therapy? Describe the first clinical case, the disorder and its cause, the earlier treatments, the procedure and its limitation.
Answer:
Gene therapy is a collection of methods that correct a gene defect diagnosed in a child or embryo by delivering a normal gene to compensate for a non-functional gene.
First case: the first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency.
Cause: the disorder results from deletion of the gene for adenosine deaminase, an enzyme crucial for the immune system.
Earlier treatments: bone marrow transplantation and enzyme replacement therapy (injected functional ADA) — but neither is completely curative.
Procedure: the patient's lymphocytes are grown in culture, a functional ADA cDNA carried by a retroviral vector is introduced, and the cells are returned to the patient.
Limitation: because the lymphocytes are not immortal, periodic infusions are required; introducing the functional gene at early embryonic stages could act as a permanent cure.
End of Section 13
You have now worked through 24 high-yield Board questions spanning tissue culture, GM and Bt crops, RNA interference, recombinant insulin, gene therapy, molecular diagnosis, transgenic animals and the ethics of biotechnology. If you can answer the five 5-markers (Q20-Q24) from memory with their key points, you have effectively secured this chapter's contribution to your paper.
Final tip: On exam day, draw and label diagrams wherever allowed — the Bt toxin action, insulin maturation, the RNAi strategy, gene therapy for ADA. Tabulate comparison-type answers and always pair a technique with its example and its practical benefit.