Biotechnology and its Applications (NEET Biology Class 12): Bt Cotton, RNAi, Insulin & Gene Therapy
Tissue Culture & Genetically Modified Crops
📌 NEET priority: Important. 2–4 questions a year. The cry gene → target pest table, the Bt toxin mechanism, RNAi, the 1983 Eli Lilly insulin route and the five uses of transgenic animals are where the marks reliably are.
Tissue culture — the foundation techniques
Term | Definition |
Explant | ANY part of a plant taken out and grown in a test tube under STERILE conditions in a special nutrient medium |
Totipotency | The capacity to generate a WHOLE PLANT from any cell or explant |
Micro-propagation | Producing THOUSANDS of plants through tissue culture in a very short duration. Used commercially for TOMATO, BANANA, APPLE |
Somaclones | The plants so produced — GENETICALLY IDENTICAL to the original plant |
Somatic hybridisation | Fusing naked PROTOPLASTS (cell walls digested away) from two different plant varieties, each with a desirable character, to get a SOMATIC HYBRID |
The nutrient medium must supply a carbon source such as sucrose, plus inorganic salts, vitamins, amino acids and growth regulators (auxins, cytokinins).
Recovering virus-free plants: even in an infected plant, the MERISTEM (apical and axillary) is FREE of virus. Culturing the meristem in vitro therefore yields virus-free plants — done successfully for banana, sugarcane and potato.
Pomato — the tomato × potato somatic hybrid — was actually achieved, but did NOT have the desired combination of characteristics for commercial use. NEET likes this cautionary detail.
Genetically Modified Organisms (GMO) — the five benefits
GM has (1) made crops tolerant to abiotic stresses (cold, drought, salt, heat); (2) reduced reliance on chemical pesticides via pest-resistant crops; (3) reduced post-harvest losses; (4) increased efficiency of mineral usage, preventing early exhaustion of soil fertility; and (5) enhanced nutritional value — e.g. GOLDEN RICE, vitamin-A enriched rice.
Bt Cotton & RNA Interference
Bt cotton — the mechanism NEET tests step by step
Some strains of Bacillus thuringiensis form protein crystals during a particular growth phase, containing a toxic insecticidal protein. These kill lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
Why the toxin doesn't kill the Bacillus itself: it exists as an INACTIVE PROTOXIN. Once an insect ingests it, the ALKALINE pH of the insect gut solubilises the crystals and converts it to the ACTIVE toxin. The activated toxin binds the midgut epithelial cell surface, creating pores that cause cell swelling and lysis, killing the insect.
cry gene | Controls |
cryIAc | Cotton BOLLWORMS |
cryIIAb | Cotton BOLLWORMS |
cryIAb | CORN BORER |
The toxin is coded by genes named cry. Most Bt toxins are insect-group SPECIFIC, so the choice of gene depends on the crop and the targeted pest. Bt crops include Bt cotton, Bt corn, rice, tomato, potato and soyabean.
RNA interference (RNAi) — pest-resistant plants
The nematode Meloidegyne incognitia infects tobacco roots and greatly reduces yield.
RNAi occurs in ALL eukaryotic organisms as a method of CELLULAR DEFENCE. It silences a specific mRNA using a complementary dsRNA that binds it and prevents translation. The natural source of such complementary RNA is infection by RNA-genome viruses or transposons (mobile genetic elements replicating via an RNA intermediate).
The strategy: using Agrobacterium vectors, nematode-specific genes were introduced into the host plant such that it produced BOTH sense AND anti-sense RNA. Being complementary, these formed dsRNA, initiating RNAi and silencing the nematode's mRNA. The parasite could not survive — the transgenic plant protected itself.
Insulin, Gene Therapy & Molecular Diagnosis
Genetically engineered insulin
Insulin has two short polypeptide chains — A and B — linked by DISULPHIDE BRIDGES. In mammals it is synthesised as a PRO-HORMONE containing an extra stretch called the C PEPTIDE, which is removed during maturation and is NOT present in mature insulin.
Insulin was earlier extracted from the pancreas of slaughtered cattle and pigs, which caused allergy and immune reactions in some patients.
In 1983, Eli Lilly (an American company) prepared two DNA sequences corresponding to chains A and B, introduced them into E. coli plasmids, produced the chains SEPARATELY, extracted them, and combined them by creating disulfide bonds to form human insulin. The main challenge was getting insulin assembled into a mature form.
Gene therapy
The first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency. ADA is crucial for immune system function; the disorder is caused by DELETION of the gene for adenosine deaminase.
Existing options are bone marrow transplantation and enzyme replacement therapy (injecting functional ADA) — but neither is completely curative.
The procedure: lymphocytes from the patient's blood are grown in culture outside the body; a functional ADA cDNA is introduced using a RETROVIRAL VECTOR; the cells are returned to the patient. Because these cells are not immortal, the patient needs PERIODIC INFUSION. A permanent cure would require introducing the gene into cells at early embryonic stages.
Molecular diagnosis
Technique | Principle | Use |
PCR | Amplification of the pathogen's nucleic acid | Detects VERY LOW concentrations of bacteria or virus BEFORE symptoms appear. Routinely used to detect HIV in suspected AIDS patients, and to detect gene mutations in suspected cancer patients |
Radioactive probe + autoradiography | A single-stranded DNA or RNA tagged with a radioactive molecule hybridises to its complementary DNA in a clone of cells | The clone with the MUTATED gene will NOT appear on the photographic film, because the probe has no complementarity with the mutated gene |
ELISA | Antigen-antibody interaction | Detects infection by the presence of ANTIGENS (proteins, glycoproteins) or by detecting ANTIBODIES synthesised against the pathogen |
Conventional methods (serum and urine analysis) cannot achieve early detection — by the time symptoms appear, pathogen concentration is already very high.
Transgenic Animals, Ethics & Why This Matters for NEET
Transgenic animals — the five reasons they are made
Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced, but over 95 per cent of all existing transgenic animals are MICE.
Purpose | What it involves | Example |
1. Normal physiology and development | Study how genes are regulated and affect normal body function | Insulin-like growth factor — introducing genes from other species that alter its formation |
2. Study of disease | Models for human diseases, enabling investigation of new treatments | Transgenic models for CANCER, CYSTIC FIBROSIS, RHEUMATOID ARTHRITIS and ALZHEIMER'S |
3. Biological products | Introduce the DNA coding for a valuable human protein | α-1-antitrypsin to treat EMPHYSEMA; attempts for PKU and cystic fibrosis. In 1997 the first transgenic cow, ROSIE, produced human protein-enriched milk (2.4 g/litre) containing human ALPHA-LACTALBUMIN — nutritionally more balanced for human babies than natural cow milk |
4. Vaccine safety | Transgenic mice test vaccine safety before human use | Testing the POLIO vaccine — could replace the use of MONKEYS for safety testing of vaccine batches |
5. Chemical safety testing | Also called toxicity/safety testing. Animals carry genes making them MORE SENSITIVE to toxic substances | Allows results to be obtained in LESS TIME |
Ethical issues, GEAC and biopiracy
The Indian Government set up the GEAC — Genetic Engineering Approval Committee — to decide on the validity of GM research and the safety of introducing GM organisms for public services.
Biopiracy is the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned.
The Basmati case: India has an estimated 200,000 varieties of rice, including 27 documented varieties of Basmati. In 1997 an American company got patent rights on Basmati rice through the US Patent and Trademark Office — a 'new' variety actually derived from Indian farmers' varieties, crossed with semi-dwarf varieties and claimed as an invention. Similar patent attempts have been made on turmeric and neem.
Why this matters for NEET
High-value one-liners: cryIAc and cryIIAb → bollworm, cryIAb → corn borer; Bt protoxin activated by ALKALINE gut pH; RNAi uses dsRNA; insulin = Eli Lilly, 1983, chains A and B joined by disulphide bridges, C peptide removed; first gene therapy 1990, ADA deficiency; Rosie, 1997, 2.4 g/L alpha-lactalbumin; 95% of transgenic animals are mice; GEAC; Basmati patent 1997.
Trap: the Bt toxin does NOT kill the Bacillus because it is an inactive protoxin — it only activates in the insect's alkaline gut. This "why doesn't it kill its own producer" question is a NEET favourite. Also, the C peptide is absent from MATURE insulin — it exists only in the pro-hormone.
Second trap: in gene therapy for ADA deficiency, the treatment is NOT a permanent cure because the engineered lymphocytes are not immortal and need periodic reinfusion — a permanent cure would need the gene introduced at the early embryonic stage. And somaclones are genetically IDENTICAL to the parent, unlike somatic hybrids which combine two different varieties.
Test Yourself: MCQs, PYQs & Active Recall
Answer these, then close the article and do an Active Recall. Reveal each answer only after you commit to one.
Practice Questions
Q1. The capacity to generate a whole plant from any cell or explant is called:
(a) Totipotency
(b) Transformation
(c) Somatic hybridisation
(d) Micro-propagation
Show answer
Answer: (a) — Totipotency is the capacity of any plant cell or explant to regenerate an entire plant.
Q2. Plants produced through tissue culture that are genetically identical to the parent are called:
(a) Somaclones
(b) Somatic hybrids
(c) Protoplasts
(d) Transgenics
Show answer
Answer: (a) — Micro-propagation produces somaclones — plants genetically identical to the original plant.
Q3. Virus-free plants can be obtained by culturing which plant part?
(a) Leaf lamina
(b) Mature stem
(c) Meristem (apical and axillary)
(d) Root tip
Show answer
Answer: (c) — Even in an infected plant the meristem is free of virus, so culturing it in vitro gives virus-free plants.
Q4. Pomato, produced by somatic hybridisation of tomato and potato:
(a) Is a transgenic plant
(b) Did not have the desired combination of characteristics for commercial use
(c) Is widely cultivated commercially
(d) Was never actually produced
Show answer
Answer: (b) — The hybrid was achieved, but it did not have all the desired combination of characteristics for commercial utilisation.
Q5. Golden rice is an example of genetic modification that:
(a) Increases drought tolerance
(b) Enhances nutritional value with vitamin A
(c) Increases pest resistance
(d) Reduces post-harvest losses
Show answer
Answer: (b) — Golden rice is vitamin A-enriched rice — an example of GM enhancing nutritional value.
Q6. Bt toxin does not kill the Bacillus that produces it because:
(a) It only affects plants
(b) It exists as an inactive protoxin, activated only by the alkaline pH of the insect gut
(c) It is stored outside the cell
(d) Bacillus has an antidote
Show answer
Answer: (b) — The toxin exists as an inactive protoxin; the alkaline pH of the insect gut solubilises the crystals and activates it.
Q7. The activated Bt toxin kills insects by:
(a) Blocking digestion of protein
(b) Binding midgut epithelial cells and creating pores causing swelling and lysis
(c) Blocking respiration
(d) Preventing moulting
Show answer
Answer: (b) — The activated toxin binds the surface of midgut epithelial cells and creates pores causing cell swelling and lysis.
Q8. The cry gene that controls the corn borer is:
(a) cryIAb
(b) cryIAc
(c) cryIIAb
(d) cryIIIA
Show answer
Answer: (a) — cryIAb controls the corn borer, while cryIAc and cryIIAb control cotton bollworms.
Q9. The nematode that infects tobacco roots, controlled using RNAi, is:
(a) Wuchereria bancrofti
(b) Caenorhabditis elegans
(c) Ascaris lumbricoides
(d) Meloidegyne incognitia
Show answer
Answer: (d) — Meloidegyne incognitia infects tobacco roots and causes a great reduction in yield.
Q10. RNA interference works by:
(a) A complementary dsRNA binding to and preventing translation of a specific mRNA
(b) Removing introns
(c) Amplifying the gene
(d) Cutting the DNA
Show answer
Answer: (a) — RNAi silences a specific mRNA because a complementary double-stranded RNA binds it and prevents translation.
Q11. RNA interference occurs naturally in eukaryotes as a method of:
(a) Gene amplification
(b) Cellular defence
(c) Protein folding
(d) DNA replication
Show answer
Answer: (b) — RNAi takes place in all eukaryotic organisms as a method of cellular defence.
Q12. Insulin consists of:
(a) Four chains as H2L2
(b) Two chains A and B linked by disulphide bridges
(c) A single polypeptide chain
(d) Three chains including C peptide
Show answer
Answer: (b) — Insulin has two short polypeptide chains, A and B, linked together by disulphide bridges.
Q13. The C peptide of pro-insulin is:
(a) Present in mature insulin
(b) A disulphide bridge
(c) Removed during maturation and absent from mature insulin
(d) The active site
Show answer
Answer: (c) — The C peptide is an extra stretch in the pro-hormone that is removed during maturation into insulin.
Q14. Human insulin was produced by recombinant DNA technology in 1983 by:
(a) Genentech
(b) Pfizer
(c) Eli Lilly
(d) Monsanto
Show answer
Answer: (c) — In 1983 Eli Lilly prepared DNA sequences for chains A and B, introduced them into E. coli plasmids and combined the chains by disulfide bonds.
Q15. The first clinical gene therapy in 1990 was given for:
(a) Adenosine deaminase (ADA) deficiency
(b) Phenylketonuria
(c) Sickle cell anaemia
(d) Cystic fibrosis
Show answer
Answer: (a) — The first clinical gene therapy was given in 1990 to a 4-year-old girl with ADA deficiency.
Q16. ADA deficiency is caused by:
(a) A point mutation
(b) Deletion of the gene for adenosine deaminase
(c) Trisomy
(d) A viral infection
Show answer
Answer: (b) — The disorder is caused due to the deletion of the gene for adenosine deaminase, an enzyme crucial for immune function.
Q17. Gene therapy for ADA deficiency requires periodic infusion because:
(a) The retrovirus is unstable
(b) The patient develops immunity
(c) The gene degrades
(d) The genetically engineered lymphocytes are not immortal
Show answer
Answer: (d) — Because the treated lymphocytes are not immortal, the patient requires periodic infusion; a permanent cure needs early embryonic introduction.
Q18. What percentage of all existing transgenic animals are mice?
(a) 50 per cent
(b) 75 per cent
(c) Over 95 per cent
(d) About 20 per cent
Show answer
Answer: (c) — Although many species have been made transgenic, over 95 per cent of all existing transgenic animals are mice.
Q19. Rosie, the first transgenic cow (1997), produced milk containing:
(a) Growth hormone
(b) Insulin
(c) Human alpha-lactalbumin at 2.4 grams per litre
(d) Alpha-1-antitrypsin
Show answer
Answer: (c) — Rosie produced human protein-enriched milk containing human alpha-lactalbumin at 2.4 grams per litre.
Q20. The committee set up by the Indian Government to decide on the validity of GM research is:
(a) ICMR
(b) NACO
(c) CSIR
(d) GEAC — Genetic Engineering Approval Committee
Show answer
Answer: (d) — GEAC makes decisions regarding the validity of GM research and the safety of introducing GM organisms for public services.
NEET Previous Year Questions (PYQs)
Real NEET previous-year questions on this chapter, with explanations in our own words.
Q21. Bt toxin crystals are toxic to which insect groups? (NEET PYQ)
(a) All arthropods equally
(b) Lepidopterans, coleopterans and dipterans
(c) Only beetles
(d) Only lepidopterans
Show answer
Answer: (b) — Bacillus thuringiensis proteins kill lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).
Q22. Alpha-1-antitrypsin produced by transgenic animals is used to treat: (NEET PYQ)
(a) Emphysema
(b) Cystic fibrosis
(c) Phenylketonuria
(d) Diabetes
Show answer
Answer: (a) — Human alpha-1-antitrypsin is used to treat emphysema; similar attempts are being made for PKU and cystic fibrosis.
Q23. Transgenic mice are being used to test the safety of which vaccine? (NEET PYQ)
(a) Polio vaccine
(b) Rabies vaccine
(c) Hepatitis-B vaccine
(d) BCG vaccine
Show answer
Answer: (a) — Transgenic mice are used to test polio vaccine safety and could replace the use of monkeys for testing vaccine batches.
Q24. Biopiracy refers to: (NEET PYQ)
(a) Use of bio-resources by organisations without proper authorisation from the countries and people concerned
(b) Illegal cloning of animals
(c) Illegal sale of GM seeds
(d) Theft of laboratory equipment
Show answer
Answer: (a) — Biopiracy is the use of bio-resources by multinational companies and other organisations without proper authorisation.
Q25. An American company obtained patent rights on Basmati rice in the year: (NEET PYQ)
(a) 1990
(b) 1983
(c) 1997
(d) 2003
Show answer
Answer: (c) — In 1997 an American company got patent rights on Basmati rice through the US Patent and Trademark Office.
Q26. The source of complementary RNA that naturally triggers RNAi could be: (NEET PYQ)
(a) Ribosomal RNA
(b) tRNA
(c) mRNA capping
(d) Infection by RNA viruses or transposons replicating via an RNA intermediate
Show answer
Answer: (d) — The source could be infection by viruses having RNA genomes or mobile genetic elements (transposons) replicating via an RNA intermediate.
Q27. PCR is routinely used in molecular diagnosis to detect: (NEET PYQ)
(a) HIV in suspected AIDS patients and mutations in suspected cancer patients
(b) Only bacterial infections
(c) Blood groups
(d) Only genetic disorders
Show answer
Answer: (a) — PCR detects very low concentrations of pathogens before symptoms appear, and is used for HIV detection and cancer gene mutations.
Q28. In the radioactive probe method of molecular diagnosis, the clone with the mutated gene: (NEET PYQ)
(a) Appears brightest on the film
(b) Cannot be cultured
(c) Will NOT appear on the photographic film
(d) Turns blue
Show answer
Answer: (c) — The probe has no complementarity with the mutated gene, so that clone does not hybridise and does not appear on the film.
Q29. The nutrient medium for plant tissue culture must contain a carbon source such as: (NEET PYQ)
(a) Glucose only
(b) Starch
(c) Cellulose
(d) Sucrose
Show answer
Answer: (d) — The medium must provide a carbon source such as sucrose, plus inorganic salts, vitamins, amino acids and growth regulators.
Q30. Naked plant cells obtained after digesting away the cell wall are called: (NEET PYQ)
(a) Protoplasts
(b) Explants
(c) Somaclones
(d) Callus
Show answer
Answer: (a) — Isolated protoplasts, surrounded only by plasma membranes, can be fused in somatic hybridisation.
Active Recall Prompt
Write everything you can recall about Biotechnology and its Applications, naming each part first: tissue culture (explant, totipotency, micro-propagation, somaclones, somatic hybridisation, virus-free plants, pomato); the five benefits of GM crops; Bt cotton (which insect groups, why the toxin doesn't kill the Bacillus, the full activation mechanism, and each cry gene with its target); RNAi (the nematode, the mechanism, the natural source of dsRNA); genetically engineered insulin (its structure, the C peptide, and the 1983 Eli Lilly route); gene therapy (the 1990 case, the full procedure, why it isn't permanent); molecular diagnosis (PCR, probes, ELISA); the five uses of transgenic animals with their examples; and ethical issues (GEAC, biopiracy, the Basmati case). Begin each fact with its topic and end it with a full stop.