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CBSE · NCERT
BIOLOGY – CHAPTER 10 : BIOTECHNOLOGY AND ITS APPLICATIONS
Chapter-wise Practice Question Paper (Board + Competitive / NEET Level)
General Instructions
- All questions are compulsory. This paper is based on NCERT Class XII Biology, Chapter 10, and includes NEET-style MCQs and Assertion–Reason questions.
- Q.1 to Q.5 are Section A (40 marks): Q.1 has 20 MCQs; Q.2, Q.3, Q.4 and Q.5 have 5 questions each; every question carries 1 mark.
- Q.6 to Q.13 carry 2 marks each; Q.14 to Q.20 carry 3 marks each; Q.21 and Q.22 are case-based questions of 4 marks each; Q.23 to Q.25 carry 5 marks each.
- Internal choice (OR) is given in Q.14 to Q.20 and Q.23 to Q.25. Attempt only one of the alternatives.
- Draw neat, labelled diagrams wherever required. Solutions to all questions are given after the paper.
SECTION – A (Objective Questions · 40 Marks)
Q.1 Choose the correct option.20 × 1 = 20
(i) Bt toxin is produced by the bacterium –
(a) Bacillus subtilis(b) Agrobacterium tumefaciens(c) Bacillus thuringiensis(d) Thermus aquaticus
(ii) The Bt toxin protein exists in Bacillus thuringiensis as –
(a) An active toxin(b) A carbohydrate(c) A lipid(d) An inactive protoxin
(iii) The Cry gene cryIAc controls the cotton bollworms, while cryIAb controls –
(a) Corn borer(b) Nematodes(c) Aphids(d) Whitefly
(iv) The Bt toxin kills the insect larva by –
(a) Blocking photosynthesis(b) Creating pores in the midgut epithelial cells, causing swelling and lysis(c) Inhibiting protein synthesis in the plant(d) Damaging the cuticle
(v) Nematode Meloidogyne incognita infects the roots of –
(a) Cotton(b) Maize(c) Tobacco plants(d) Rice
(vi) RNA interference (RNAi) involves –
(a) Silencing of a specific mRNA by a complementary dsRNA molecule that binds to it and prevents translation(b) Synthesis of mRNA from DNA(c) Joining of two RNA molecules(d) Translation of mRNA
(vii) ‘Golden rice’ is rich in –
(a) Vitamin C(b) Iron(c) Protein(d) Vitamin A (β-carotene)
(viii) The first transgenic cow, Rosie, produced milk containing the human protein –
(a) α-lactalbumin(b) Insulin(c) Casein(d) Growth hormone
(ix) Insulin is made up of two short polypeptide chains, A and B, linked together by –
(a) Peptide bonds(b) Hydrogen bonds(c) Disulphide bridges(d) Ionic bonds
(x) The company that first produced human insulin by recombinant DNA technology in 1983 was –
(a) Cipla(b) Eli Lilly(c) Ranbaxy(d) Pfizer
(xi) Gene therapy was first used in 1990 to correct –
(a) Cystic fibrosis(b) Haemophilia(c) Phenylketonuria(d) Adenosine deaminase (ADA) deficiency
(xii) In ADA deficiency, in the first step of the treatment, the patient's lymphocytes are –
(a) Killed(b) Grown in a culture outside the body, and a functional ADA cDNA is introduced using a retroviral vector(c) Removed permanently(d) Injected with enzyme
(xiii) A permanent cure for ADA deficiency is possible if the gene isolated from bone-marrow cells is introduced into –
(a) Cells at early embryonic stages(b) Red blood cells(c) Platelets(d) Neurons
(xiv) A technique that detects the presence of antigens or the antibodies synthesised against pathogens is –
(a) PCR(b) ELISA(c) Gel electrophoresis(d) Northern blotting
(xv) For early detection of a pathogen such as HIV in suspected AIDS patients, the technique used is –
(a) Gel electrophoresis(b) Tissue culture(c) Polymerase chain reaction (PCR)(d) Karyotyping
(xvi) A single-stranded DNA or RNA tagged with a radioactive molecule is used to detect mutations in genes in suspected cancer patients. It is called a –
(a) Primer(b) Plasmid(c) Vector(d) Probe
(xvii) About 95 per cent of all existing transgenic animals are –
(a) Mice(b) Rabbits(c) Pigs(d) Sheep
(xviii) The organisation set up by the Indian Government to make decisions about the validity of GM research and the safety of introducing GM organisms for public services is –
(a) ICMR(b) CSIR(c) GEAC (Genetic Engineering Appraisal Committee)(d) NEERI
(xix) The use of bio-resources by multinational companies and other organisations without proper authorisation from the countries concerned is called –
(a) Biofortification(b) Biopiracy(c) Bioremediation(d) Biomagnification
(xx) Which of the following is NOT a benefit of genetically modified crops?
(a) Reduced use of chemical pesticides(b) Enhanced nutritional value of food(c) Increased tolerance to abiotic stresses(d) Increased dependence on chemical fertilisers
Q.2 Fill in the blanks.5 × 1 = 5
(i) The Bt toxin gene was isolated from the bacterium ______.
(ii) The first clinical gene therapy was given to correct the deficiency of the enzyme ______.
(iii) The technique based on the principle of antigen–antibody interaction is called ______.
(iv) The first transgenic cow, ‘Rosie’, produced the human protein ______ in her milk.
(v) Use of bio-resources without proper authorisation from the concerned country is called ______.
Q.3 Write True or False.5 × 1 = 5
(i) Bt toxin kills the insect by creating pores in the midgut epithelial cells.
(ii) The insulin produced from E. coli contains the C peptide.
(iii) RNA interference (RNAi) works by silencing a specific mRNA with a complementary dsRNA.
(iv) PCR can be used for early detection of HIV.
(v) Transgenic animals are used only for producing milk.
Q.4 Match Column ‘A’ with Column ‘B’.5 × 1 = 5
| Column ‘A’ | Column ‘B’ |
|---|---|
| (i) Bt cotton | (a) Gene therapy |
| (ii) Golden rice | (b) Vitamin A rich |
| (iii) Rosie | (c) Antigen–antibody interaction |
| (iv) ADA deficiency | (d) Insect resistant |
| (v) ELISA | (e) Transgenic cow |
Q.5 Assertion (A) – Reason (R) type questions. Choose: (a) Both A and R true, R explains A; (b) Both true, R does not explain A; (c) A true, R false; (d) A false, R true.5 × 1 = 5
(i) Assertion (A): Bt toxin does not kill the Bacillus thuringiensis bacterium that produces it.
Reason (R): The toxin exists in the bacterium as an inactive protoxin.
Reason (R): The toxin exists in the bacterium as an inactive protoxin.
(ii) Assertion (A): In gene therapy for ADA deficiency, the lymphocytes must be given to the patient periodically.
Reason (R): Lymphocytes from the patient's blood are not immortal.
Reason (R): Lymphocytes from the patient's blood are not immortal.
(iii) Assertion (A): PCR is used for the early detection of HIV infection.
Reason (R): ELISA detects the antibodies against the pathogen.
Reason (R): ELISA detects the antibodies against the pathogen.
(iv) Assertion (A): Mature insulin contains the C peptide.
Reason (R): Insulin is synthesised in humans as a pro-hormone.
Reason (R): Insulin is synthesised in humans as a pro-hormone.
(v) Assertion (A): Transgenic animals are used for testing the safety of vaccines.
Reason (R): Transgenic mice are used to test the safety of the polio vaccine before it is used on humans.
Reason (R): Transgenic mice are used to test the safety of the polio vaccine before it is used on humans.
SECTION – B (Very Short Answer · 2 Marks each)
6. What are genetically modified organisms (GMOs)? Mention any two benefits of GM crops.(2)
7. How is the Bt toxin protein prevented from killing the bacterium that produces it?(2)
8. What is RNA interference? How was it used to protect tobacco plants from nematode infestation?(2)
9. Name the cells of the immune system that are used in the ADA gene therapy. Why is it not a permanent cure?(2)
10. What is the principle of ELISA?(2)
11. What are transgenic animals? State any two uses.(2)
12. What is biopiracy? Give an example.(2)
13. What is the role of GEAC?(2)
SECTION – C (Short Answer · 3 Marks each)
14. Explain how Bt cotton is protected against insect pests.(3)
OR
Explain how pest-resistant plants (RNAi) are made against the nematode Meloidogyne incognita.
15. Describe how human insulin is produced by recombinant DNA technology.(3)
OR
Why is insulin produced by rDNA technology preferred to the insulin obtained from animals?
16. Describe the steps of gene therapy with a suitable example.(3)
OR
What is gene therapy? Explain with reference to ADA deficiency.
17. Explain the molecular diagnosis methods: PCR, ELISA and probe hybridisation.(3)
OR
How can a disease be diagnosed at an early stage? Explain with two techniques.
18. What are transgenic animals? Describe four of their applications.(3)
OR
Describe the biological products and safety-testing uses of transgenic animals.
19. What are the ethical issues related to biotechnology? Write about GEAC.(3)
OR
What is biopiracy? Explain with examples and mention the steps India has taken.
20. List three applications of biotechnology in agriculture and explain any one.(3)
OR
Mention the advantages of GM crops in agriculture and give examples.
SECTION – D (Case-Based Questions · 4 Marks each)
21. Read the passage and answer the questions that follow.(4)
Bt cotton is a genetically modified crop that contains a gene from the bacterium Bacillus thuringiensis. The gene produces a crystal protein, which is toxic to some insect larvae. Farmers growing Bt cotton need to spray much less pesticide.
(i) Name the gene used in Bt cotton to control the cotton bollworms.(1)
(ii) Why does the Bt toxin not kill the bacterium that makes it?(1)
(iii) Explain how the toxin kills the insect larva. State one advantage of Bt cotton.(2)
22. Read the passage and answer the questions that follow.(4)
A four-year-old girl is suffering from a disease in which the immune system does not work because the enzyme adenosine deaminase is missing. In 1990, doctors took her lymphocytes, grew them outside the body, inserted a functional gene using a retrovirus, and returned them to her body.
(i) Name the disease.(1)
(ii) What is the name of the treatment given to the girl?(1)
(iii) Why was it necessary to repeat the infusion of the cells? Suggest a permanent cure.(2)
SECTION – E (Long Answer · 5 Marks each)
23. Describe the applications of biotechnology in agriculture: Bt crops, RNAi and other GM crops.(5)
OR
Describe the applications of biotechnology in medicine: genetically engineered insulin, gene therapy, molecular diagnosis and transgenic animals.
24. Explain the production of Bt cotton and describe its mode of action. Also write the advantages and concerns of GM crops.(5)
OR
Explain RNA interference, with the example of nematode-resistant tobacco, and the use of Agrobacterium vectors.
25. Describe the process of human insulin production by recombinant DNA technology and the importance of gene therapy.(5)
OR
Write notes on: (a) Transgenic animals, (b) Ethical issues in biotechnology, (c) Biopiracy and patents.
********
CBSE · NCERT
BIOLOGY – CHAPTER 10 : COMPLETE SOLUTIONS
Biotechnology and its Applications · Answer Key with Step-by-Step Explanations
Q.1 Quick Answer Key (MCQ)20 × 1 = 20
| i | (c) | ii | (d) | iii | (a) | iv | (b) | v | (c) |
| vi | (a) | vii | (d) | viii | (a) | ix | (c) | x | (b) |
| xi | (d) | xii | (b) | xiii | (a) | xiv | (b) | xv | (c) |
| xvi | (d) | xvii | (a) | xviii | (c) | xix | (b) | xx | (d) |
Q.1 Solutions with Explanation
(i) Ans. (c) Bacillus thuringiensis
Bacillus thuringiensis forms protein crystals (Cry proteins) during a particular phase of its growth; these are toxic to certain insects.
(ii) Ans. (d) An inactive protoxin
It is an inactive protoxin; it is converted into an active toxin in the alkaline pH of the insect gut, which solubilises the crystals.
(iii) Ans. (a) Corn borer
cryIAc and cryIIAb – cotton bollworms; cryIAb – corn borer.
(iv) Ans. (b) Creating pores in the midgut epithelial cells, causing swelling and lysis
The active toxin binds to the midgut epithelial cells, creates pores, and the cells swell and burst, killing the insect.
(v) Ans. (c) Tobacco plants
It causes a great reduction in yield of tobacco; RNA interference (RNAi) was used to make the plants resistant.
(vi) Ans. (a) Silencing of a specific mRNA by a complementary dsRNA molecule that binds to it and prevents translation
A complementary dsRNA binds to and silences the mRNA; it is a method of cellular defence found in all eukaryotes, used in the tobacco plant against the nematode.
(vii) Ans. (d) Vitamin A (β-carotene)
Golden rice is a GM variety with β-carotene (provitamin A) genes; it helps to overcome vitamin A deficiency.
(viii) Ans. (a) α-lactalbumin
The milk contained human α-lactalbumin (2.4 g per litre), more nutritionally balanced for human babies than natural cow milk.
(ix) Ans. (c) Disulphide bridges
In mature insulin the chains A (21 amino acids) and B (30 amino acids) are linked by disulphide bridges; the C peptide of pro-insulin is removed.
(x) Ans. (b) Eli Lilly
Eli Lilly prepared two DNA sequences corresponding to the A and B chains and introduced them into E. coli to produce the chains separately; they were then combined by disulphide bonds.
(xi) Ans. (d) Adenosine deaminase (ADA) deficiency
It was given to a four-year-old girl with ADA deficiency, which affects the immune system.
(xii) Ans. (b) Grown in a culture outside the body, and a functional ADA cDNA is introduced using a retroviral vector
The lymphocytes are grown in culture, the functional ADA cDNA is introduced by a retroviral vector, and the cells are returned to the patient; they are not immortal, so periodic infusions are needed.
(xiii) Ans. (a) Cells at early embryonic stages
Gene introduced into early embryonic stage cells would be a permanent cure.
(xiv) Ans. (b) ELISA
Enzyme-linked immunosorbent assay (ELISA) is based on the principle of antigen–antibody interaction.
(xv) Ans. (c) Polymerase chain reaction (PCR)
PCR amplifies the nucleic acid of the pathogen (even in very low concentration) before the symptoms appear.
(xvi) Ans. (d) Probe
The probe hybridises with its complementary DNA, and the clone is detected by autoradiography; the mutated gene does not appear on the photographic film.
(xvii) Ans. (a) Mice
Transgenic mice are used mainly for testing vaccine safety, studying disease and chemical safety (toxicity) testing.
(xviii) Ans. (c) GEAC (Genetic Engineering Appraisal Committee)
GEAC (now Genetic Engineering Appraisal Committee) evaluates the safety of GM research and its introduction.
(xix) Ans. (b) Biopiracy
Biopiracy; e.g. patents on Basmati rice, turmeric and neem-based products were challenged by India.
(xx) Ans. (d) Increased dependence on chemical fertilisers
GM crops are aimed at reducing, not increasing, the dependence on chemical fertilisers and pesticides; they also reduce post-harvest losses.
Q.2 Fill in the blanks5 × 1 = 5
(i) Bacillus thuringiensis
(ii) Adenosine deaminase (ADA)
(iii) ELISA
(iv) Human α-lactalbumin
(v) Biopiracy
Q.3 True / False5 × 1 = 5
(i) True.
The cells swell and burst after the pores form.
(ii) False.
The C peptide is absent in mature insulin; the A and B chains are produced separately and linked by disulphide bridges.
(iii) True.
It prevents translation of the mRNA.
(iv) True.
It amplifies the viral nucleic acid even in very low concentration.
(v) False.
They are also used for vaccine safety, chemical safety testing and studying diseases and normal physiology.
Q.4 Matching5 × 1 = 5
(i) – (d) · (ii) – (b) · (iii) – (e) · (iv) – (a) · (v) – (c)
Bt cotton – insect resistant; golden rice – rich in vitamin A; Rosie – transgenic cow; ADA deficiency – gene therapy; ELISA – antigen–antibody interaction.
Q.5 Assertion – Reason5 × 1 = 5
(i) Ans. (a)
Both true; the protoxin is activated only in the alkaline gut of the insect, so the bacterium is not harmed.
(ii) Ans. (a)
Both true; the cells have a limited life span, so periodic infusion is needed.
(iii) Ans. (b)
Both are true, but R does not explain A – PCR amplifies the nucleic acid of the virus.
(iv) Ans. (d)
A is false (the C peptide is removed during maturation); R is true.
(v) Ans. (a)
Both true; the use of transgenic mice reduces the cost and time of the safety tests.
SECTION – B (2 Marks each)
6. Ans.
Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called genetically modified organisms. [1] Benefits: more tolerant to abiotic stresses (cold, drought, salt, heat); reduced reliance on chemical pesticides; reduced post-harvest losses; enhanced nutritional value (golden rice); efficient use of mineral nutrients. (Any two) [½ + ½]
7. Ans.
The Bt toxin is produced as an inactive protoxin in the bacterium. [1] It is converted into the active form only in the alkaline pH of the insect gut, where the crystals are solubilised; so the bacterium is not harmed. [1]
8. Ans.
RNAi is a process of silencing a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA. [1] Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant, producing sense and antisense RNA; these formed dsRNA that silenced the nematode's specific mRNA, so the parasite could not survive in the transgenic host. [1]
9. Ans.
Lymphocytes from the patient's blood are used. [1] They are not immortal, so periodic infusions are needed; the cure would be permanent only if the gene is introduced into the cells of early embryonic stages (bone-marrow cells). [1]
10. Ans.
ELISA – enzyme-linked immunosorbent assay – is based on the principle of antigen–antibody interaction. [1] Infection by a pathogen is detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen. [1]
11. Ans.
Animals whose DNA has been manipulated to possess and express an extra (foreign) gene are called transgenic animals. [1] Uses: normal physiology and development; study of disease; biological products (human α-lactalbumin); vaccine safety; chemical safety testing. (Any two) [½ + ½]
12. Ans.
Biopiracy is the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned, without compensatory payment. [1] Example: a US company got a patent on Basmati rice (varieties of Indian farmers); patents on turmeric and neem were also challenged. [1]
13. Ans.
The Genetic Engineering Appraisal Committee (GEAC) has been set up by the Government of India to make decisions regarding the validity of GM research and the safety of introducing GM organisms for public services. [2]
SECTION – C (3 Marks each)
14. Ans.
Bacillus thuringiensis forms protein crystals containing an insecticidal protein (Cry protein), which exists as an inactive protoxin. [1] Specific Bt toxin genes (cryIAc, cryIIAb) were isolated and incorporated into cotton plants. [1] When the insect larva feeds, the protoxin is activated in the alkaline gut, binds to the midgut epithelial cells, creates pores, cells swell and lyse, and the insect dies. [1]
OR
The nematode Meloidogyne incognita infects tobacco roots and greatly reduces the yield. [1] Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant; the genes produced sense and antisense RNA in the host cells, which, being complementary, formed double-stranded RNA (dsRNA) that initiated RNAi and silenced the specific mRNA of the nematode. [1] The parasite could not live in the transgenic host, so the plant was protected. [1]
15. Ans.
Insulin consists of two short polypeptide chains: chain A and chain B, linked together by disulphide bridges. [1] In humans, it is synthesised as a pro-hormone that contains an extra stretch called the C peptide, which is removed during maturation. [1] In 1983, Eli Lilly prepared two DNA sequences corresponding to the A and B chains of human insulin and introduced them into E. coli to produce the chains separately; these were extracted and combined by creating disulphide bonds to form human insulin. [1]
OR
Earlier, insulin was extracted from the pancreas of slaughtered cattle and pigs; it caused allergy or some other type of reaction in some patients because it was a foreign protein. [1½] The rDNA insulin (e.g. Humulin) is identical to human insulin, is produced in large quantity, is free from such reactions, and avoids the use of animals. [1½]
16. Ans.
Gene therapy is a collection of methods that allows the correction of a gene defect diagnosed in a child or embryo: genes are inserted into a person's cells and tissues to treat a disease. [1] The first clinical gene therapy (1990) was given to a 4-year-old girl with adenosine deaminase (ADA) deficiency; this enzyme is crucial for the functioning of the immune system. [1] Lymphocytes from the patient's blood were grown in a culture; a functional ADA cDNA (using a retroviral vector) was introduced into them and the cells were returned to the patient. [1]
OR
Gene therapy is the insertion of a normal gene to correct a gene defect. [1] ADA deficiency – a disorder caused by deletion of the gene for the enzyme adenosine deaminase; the child cannot develop an immune response and may die. [1] Treatments: bone marrow transplantation, enzyme replacement therapy (injection of functional ADA), or gene therapy – introduction of the functional ADA cDNA into lymphocytes (or, as a permanent cure, into the early embryonic cells). [1]
17. Ans.
PCR: amplification of the nucleic acid of the pathogen (e.g. HIV in suspected AIDS patients) even in a very low concentration; also used to detect mutations in genes in suspected cancer patients. [1] ELISA: based on antigen–antibody interaction – detects the antigens or the antibodies synthesised against the pathogen. [1] Probe: a single-stranded DNA or RNA tagged with a radioactive molecule hybridises to its complementary DNA in a clone of cells, followed by detection by autoradiography. [1]
OR
Conventional methods (serum and urine analysis) can detect a disease only when the symptoms appear and the pathogen is in a large number. [1] PCR detects the pathogen's nucleic acid (e.g. HIV) at a very early stage when the number of pathogens is low. [1] ELISA detects the antigen or the antibodies against the pathogen. [1]
18. Ans.
Transgenic animals are animals whose DNA has been manipulated to possess and express a foreign gene. [1] Applications: (1) Normal physiology and development – study of gene regulation and its effect on the normal functions of the body (e.g. insulin-like growth factor); (2) Study of disease – models for cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's; (3) Biological products – e.g. human α-lactalbumin from the transgenic cow Rosie; (4) Vaccine safety – e.g. transgenic mice for the polio vaccine; (5) Chemical safety testing (toxicity). (Any four) [½ × 4]
OR
Biological products: medicines needed for certain human diseases are produced by transgenic animals, e.g. α-1-antitrypsin used to treat emphysema; products for phenylketonuria and cystic fibrosis. In 1997 the first transgenic cow, Rosie, produced human α-lactalbumin-enriched milk (2.4 g/L). [1½] Vaccine safety: transgenic mice are used to test the safety of the polio vaccine; if successful, the number of animals used and time can be reduced. [½] Chemical safety testing: transgenic animals made more sensitive to toxic substances than non-transgenic animals are exposed to the toxic substances and the effects studied; they give results in a shorter time. [1]
19. Ans.
Manipulation of living organisms by human beings is not always acceptable: ethical standards are needed to evaluate the morality of all human activities that might help or harm living organisms. [1] Biological significance and unpredictable consequences of GMOs, and the patenting of biological material, raise concerns. [1] GEAC (Genetic Engineering Appraisal Committee) makes decisions on the validity of GM research and the safety of introducing GM organisms for public services. [1]
OR
Biopiracy: the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned, without compensatory payment. [1] Examples: US patents on Basmati rice, turmeric and neem-based products were granted and later challenged; most of the Basmati varieties are of Indian origin. [1] The Indian Parliament has cleared the second amendment of the Indian Patents Bill, which takes care of patent terms, emergency provisions and research and development initiatives. [1]
20. Ans.
(i) Production of GM crops with Bt toxin; (ii) pest-resistant plants using RNAi; (iii) crops with enhanced nutritional value such as golden rice. [1] Golden rice is a variety genetically modified to produce β-carotene (provitamin A), which helps to overcome vitamin A deficiency. [1] Flavr Savr tomato has a longer shelf life – a delayed ripening. [1]
OR
Advantages: (i) crops more tolerant to abiotic stresses (cold, drought, salt, heat); (ii) reduced reliance on chemical pesticides (pest-resistant crops); (iii) reduced post-harvest losses; (iv) increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of the soil); (v) enhanced nutritional value of food, e.g. golden rice. [2] Examples: Bt cotton, Bt corn, Bt brinjal, golden rice, Flavr Savr tomato. [1]
SECTION – D (Case-Based · 4 Marks each)
21. Ans.
(i) cryIAc (and cryIIAb) genes. [1]
(ii) The toxin is formed as an inactive protoxin, activated only in the alkaline pH of the insect gut. [1]
(iii) The activated toxin binds to the midgut epithelial cells and creates pores; cells swell and lyse, causing the death of the larva. [1] Advantage: reduces the use of chemical pesticides (cheaper and safer for the environment) and so improves yield. [1] [2]
22. Ans.
(i) Adenosine deaminase (ADA) deficiency. [1]
(ii) Gene therapy – the first clinical gene therapy. [1]
(iii) Lymphocytes are not immortal and have a limited life span, so periodic infusions were needed. [1] A permanent cure is possible if the gene isolated from bone-marrow cells is introduced into cells at early embryonic stages. [1] [2]
SECTION – E (Long Answer · 5 Marks each)
23. Ans.
Agricultural applications: GM crops are more tolerant to abiotic stresses, reduce the use of pesticides, reduce post-harvest losses, use minerals efficiently and have enhanced nutritional value. [1]
Bt crops: Bt toxin genes (cryIAc, cryIIAb – cotton bollworms; cryIAb – corn borer) from Bacillus thuringiensis; the inactive protoxin is activated in the alkaline gut of the insect, creates pores in the midgut cells, which swell and lyse. [2]
RNAi: the nematode Meloidogyne incognita is controlled in tobacco; dsRNA from sense and antisense RNAs silences the mRNA of the nematode (via Agrobacterium vector). [1]
Others: Golden rice (β-carotene), Flavr Savr tomato. [1]
Bt crops: Bt toxin genes (cryIAc, cryIIAb – cotton bollworms; cryIAb – corn borer) from Bacillus thuringiensis; the inactive protoxin is activated in the alkaline gut of the insect, creates pores in the midgut cells, which swell and lyse. [2]
RNAi: the nematode Meloidogyne incognita is controlled in tobacco; dsRNA from sense and antisense RNAs silences the mRNA of the nematode (via Agrobacterium vector). [1]
Others: Golden rice (β-carotene), Flavr Savr tomato. [1]
OR
Insulin: two chains A and B linked by disulphide bridges; the pro-insulin contains the C peptide, which is removed; Eli Lilly (1983) made the A and B chain DNA and expressed them in E. coli separately, then combined them. [1½]
Gene therapy: correction of a gene defect; 1990 – ADA deficiency, lymphocytes cultured with ADA cDNA introduced by a retroviral vector; permanent cure by introducing the gene into the early embryonic cells. [1½]
Molecular diagnosis: PCR (early detection of HIV and cancer mutations), ELISA (antigen–antibody interaction), probe hybridisation (radioactive ssDNA, autoradiography). [1]
Transgenic animals: Rosie (α-lactalbumin), vaccine safety, chemical safety testing, study of disease. [1]
Gene therapy: correction of a gene defect; 1990 – ADA deficiency, lymphocytes cultured with ADA cDNA introduced by a retroviral vector; permanent cure by introducing the gene into the early embryonic cells. [1½]
Molecular diagnosis: PCR (early detection of HIV and cancer mutations), ELISA (antigen–antibody interaction), probe hybridisation (radioactive ssDNA, autoradiography). [1]
Transgenic animals: Rosie (α-lactalbumin), vaccine safety, chemical safety testing, study of disease. [1]
24. Ans.
Production: Bt toxin genes (cryIAc, cryIIAb) isolated from Bacillus thuringiensis are incorporated into the cotton plants using a vector. [1]
Mode of action: the toxin is produced as an inactive protoxin; in the alkaline gut of the larva it is activated; it binds to the midgut epithelial cells and forms pores; cells swell and burst; the larva dies. [2]
Advantages: less pesticide use, higher yield, reduced loss. [1]
Concerns: effect on non-target organisms, gene flow to wild relatives, allergenicity, ethical issues, biopiracy and patents; GEAC checks the safety of GM crops. [1]
Mode of action: the toxin is produced as an inactive protoxin; in the alkaline gut of the larva it is activated; it binds to the midgut epithelial cells and forms pores; cells swell and burst; the larva dies. [2]
Advantages: less pesticide use, higher yield, reduced loss. [1]
Concerns: effect on non-target organisms, gene flow to wild relatives, allergenicity, ethical issues, biopiracy and patents; GEAC checks the safety of GM crops. [1]
OR
RNAi: a cellular defence found in all eukaryotes; silencing of a specific mRNA by a complementary dsRNA that binds to it and prevents translation. Source of the dsRNA may be an infection by viruses having an RNA genome or mobile genetic elements (transposons). [2]
Nematode-resistant tobacco: Meloidogyne incognita infects tobacco roots and reduces yield; using Agrobacterium vectors, the nematode-specific genes were introduced into the host plant; the DNA was such that it produced both sense and antisense RNA in the host cells; being complementary to each other, the two RNAs formed a dsRNA that initiated RNAi and silenced the nematode-specific mRNA. [2]
Result: the parasite could not survive in the transgenic host expressing the specific interfering RNA; the transgenic plant was thus protected. [1]
Nematode-resistant tobacco: Meloidogyne incognita infects tobacco roots and reduces yield; using Agrobacterium vectors, the nematode-specific genes were introduced into the host plant; the DNA was such that it produced both sense and antisense RNA in the host cells; being complementary to each other, the two RNAs formed a dsRNA that initiated RNAi and silenced the nematode-specific mRNA. [2]
Result: the parasite could not survive in the transgenic host expressing the specific interfering RNA; the transgenic plant was thus protected. [1]
25. Ans.
Insulin: the pancreas secretes insulin (in diabetes, it is not enough). Earlier, it was extracted from the pancreas of slaughtered cattle and pigs and could cause allergy. [1] Mature insulin has chains A (21 amino acids) and B (30 amino acids) linked by disulphide bridges; pro-insulin has the extra C peptide, which is removed. [1] In 1983 Eli Lilly prepared the DNA sequences of A and B, introduced them separately in plasmids of E. coli, produced the chains, extracted and combined them by disulphide bonds. [1]
Gene therapy: correction of the gene defect; ADA deficiency (1990) – cultured lymphocytes with functional ADA cDNA introduced by a retroviral vector; periodic infusions; permanent cure only by gene introduced in early embryonic cells. [2]
Gene therapy: correction of the gene defect; ADA deficiency (1990) – cultured lymphocytes with functional ADA cDNA introduced by a retroviral vector; periodic infusions; permanent cure only by gene introduced in early embryonic cells. [2]
OR
(a) Transgenic animals: animals whose DNA has been manipulated to express a foreign gene; 95% are mice; used in normal physiology, disease study, biological products (Rosie – α-lactalbumin), vaccine safety, chemical safety testing. [2]
(b) Ethical issues: ethical standards are needed to evaluate the morality of the manipulation of living organisms; unpredictable consequences of GMOs; the Indian Government has set up GEAC to check the validity of GM research and the safety of GM organisms for public services. [1½]
(c) Biopiracy and patents: use of bio-resources without authorisation and compensation; patents on Basmati, turmeric and neem were challenged by India; a patent gives the inventor the sole right to a product or process; the Indian Patents Bill has been amended. [1½]
(b) Ethical issues: ethical standards are needed to evaluate the morality of the manipulation of living organisms; unpredictable consequences of GMOs; the Indian Government has set up GEAC to check the validity of GM research and the safety of GM organisms for public services. [1½]
(c) Biopiracy and patents: use of bio-resources without authorisation and compensation; patents on Basmati, turmeric and neem were challenged by India; a patent gives the inventor the sole right to a product or process; the Indian Patents Bill has been amended. [1½]
QUICK REVISION · HIGH-YIELD POINTS (NEET / CBSE)
- GMOs: plants, bacteria, fungi, animals whose genes are altered. Benefits: abiotic stress tolerance, less pesticide, less post-harvest loss, better mineral use, better nutrition (golden rice – β-carotene).
- Bt toxin: Bacillus thuringiensis; cry genes – cryIAc, cryIIAb (cotton bollworm), cryIAb (corn borer); inactive protoxin → active in alkaline insect gut → pores in midgut cells → lysis.
- RNAi: silencing of mRNA by complementary dsRNA; Meloidogyne incognita (nematode) in tobacco; Agrobacterium vector; sense + antisense RNA.
- Insulin: chains A (21 aa) + B (30 aa) joined by disulphide bridges; C peptide removed in mature insulin; Eli Lilly (1983) – separate chains in E. coli; Humulin.
- Gene therapy: first in 1990, ADA deficiency (4-year-old girl); lymphocytes + ADA cDNA via retroviral vector; not permanent – cells not immortal; permanent cure – early embryonic cells.
- Molecular diagnosis: PCR (early HIV, cancer mutations), ELISA (antigen–antibody), probe (radioactive ssDNA/RNA + autoradiography).
- Transgenic animals: 95% mice; Rosie (1997) – human α-lactalbumin, 2.4 g/L; uses – physiology, disease models, biological products, vaccine safety, chemical toxicity testing.
- Ethics: GEAC – Genetic Engineering Appraisal Committee decides validity and safety of GM research and GMOs.
- Biopiracy: use of bio-resources without authorisation/compensation; Basmati, turmeric and neem patents; Indian Patents Bill amended.
- Golden rice – vitamin A; Flavr Savr tomato – delayed ripening; Bt cotton, Bt brinjal, Bt corn – insect resistance.
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