How do I organise the whole Biotech Applications chapter? Also how does Bt toxin kill the insect but not the bacterium?
Nisha Verma12th Sample
16 Oct 2026 · 1 min read
Biotechnology and its Applications. After the principles chapter (cloning, vectors, bioreactors), this one is the "what do we use it for" chapter and I'm drowning in examples: Bt cotton, RNAi, golden rice, insulin, gene therapy, ADA, transgenic animals, biopiracy.
How I'm planning to organise it: agriculture, medicine, animals, and ethical issues. But I'd like to check that my sub-lists are correct and that nothing important is missing.
Two points where I want an actual explanation:
- Bt toxin. NCERT says Bacillus thuringiensis produces proteins that kill certain insects (cry genes like cryIAc, cryIIAb). If the bacterium makes a toxin that kills insects, why does it not kill itself, and why doesn't it harm the Bt cotton plant that makes it?
- Insulin. I know recombinant human insulin is made in E. coli. But I remember the NCERT diagram had A and B chains, a C peptide and disulphide bonds. Why can't we just put the insulin gene in the bacterium and be done?
I have my own sheet already but would love to hear how others structure it.
6 answers & replies
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[+][–]Tanvi Deshmukh12thSample· 3d ago
Your four boxes are right! My sheet:
Agriculture (GM crops): more tolerant to abiotic stresses (cold, drought, salt, heat); less reliance on chemical pesticides (pest-resistant crops); reduced post-harvest losses; increased efficiency of mineral usage (prevents early exhaustion of soil fertility); enhanced nutritional value (golden rice = vitamin A); tailor-made plants for starches, fuels, pharmaceuticals. Specifics: Bt cotton, RNAi against the nematode in tobacco roots. Medicine: recombinant insulin, other proteins, gene therapy (ADA deficiency), molecular diagnosis (PCR, ELISA, probes). Animals: transgenic animals. Ethics: GEAC (Genetic Engineering Appraisal Committee), biopiracy and patents.
I'd say nothing is missing, just add vaccines under medicine!!
[+][–]Zoya Khan12thSample· 3d ago
Bt toxin: the crystals made by Bacillus thuringiensis contain the toxic protein in an inactive form (protoxin). It is harmless as such. When an insect eats it, the alkaline pH of the insect's gut dissolves the crystals and activates the toxin. The activated toxin binds to the surface of midgut epithelial cells and creates pores, the cells swell and burst (lysis), and the insect dies. So the bacterium is safe because the toxin is stored inactive, and the cotton plant is safe because the plant's own cells don't have this gut-type alkaline activation either. Different cry genes target different insects: cryIAc and cryIIAb for cotton bollworms, cryIAb for corn borer.
[+][–]Mehak AroraDropperSample· 3d ago
For insulin, E. coli can just make the whole thing: you put the gene for the insulin precursor (proinsulin) into E. coli, and the bacterium then trims the C peptide away automatically, just like our body does, and you get mature insulin directly. So the A and B chains are just a diagram thing.
[+][–]Rahul DubeyDropperSample· 3d ago
Mehak, that is not what the book describes, and the reason matters. In humans, insulin is made as proinsulin (A chain, B chain and a C peptide in between). The C peptide is removed during maturation by processing machinery that E. coli doesn't have. NCERT: the A and B chains were made as separate DNA sequences and put into E. coli plasmids; the chains were produced separately, extracted, and then combined by creating disulphide bonds to form human insulin. That's the whole trick, skip the C peptide.
[+][–]Nisha Verma12thSample· 3d agoAuthor
that clears it, thank you. "Skip the C peptide, join the two chains" is the sentence I'll write in the test. And the Bt protoxin answer is exactly what I wanted too.
[+][–]Kavya NaikDropperSample· 3d ago
Gene therapy and ADA, since it's a NEET favourite: ADA (adenosine deaminase) is crucial for the immune system, and its deficiency in a child (first clinical gene therapy, 1990, a 4-year-old girl) was treated by taking lymphocytes from the patient's blood, growing them in culture outside the body, introducing a functional ADA cDNA using a retroviral vector, and returning them to the patient. It is not a permanent cure, because these cells are not immortal, so periodic infusion is needed. If a gene from marrow cells is introduced early in embryonic stages, it could be a permanent cure.
And transgenic animals: over 95% of all existing transgenic animals are mice. Uses: studying normal physiology and gene regulation, disease models, biological products, vaccine safety testing and chemical safety (toxicity) testing.
