How a Bacterial Gene Protects Cotton From Bollworms
Explore how biotechnology produces Bt crops, pest-resistant plants through RNA interference and vitamin-rich golden rice, human insulin, gene therapy and molecular diagnosis, and transgenic animals, along with biosafety, biopiracy and biopatents.
How is biotechnology changing farms and hospitals?
The same cut-and-paste tools used in laboratories now protect crops from pests, make human insulin in bacteria, detect infections early and create animals that make medicines. With that power come questions about safety and about who owns living resources.
This lesson covers biotechnology in agriculture and medicine, transgenic animals, and biosafety and biopiracy.
This lesson covers biotechnology in agriculture and medicine, transgenic animals, and biosafety and biopiracy.
How do Bt crops, RNA interference and golden rice use biotechnology in agriculture?
Bt crops carry a bacterial gene for an insect-killing protein, RNA interference silences an essential gene of a pest, and golden rice is engineered to make beta-carotene, a source of vitamin A.
Genetically modified crops can:
- Resist pests and reduce the use of chemical pesticides
- Tolerate drought, cold, salt and heat
- Reduce losses after harvest and carry better nutrition
Bt crops:
- The bacterium Bacillus thuringiensis makes crystal Bt toxin proteins
- The toxin is an inactive protoxin; in the alkaline gut of an insect it becomes active, binds the gut lining, creates pores and kills the insect
- The toxin genes are called cry genes — proteins coded by cryIAc and cryIIAb control cotton bollworms, and cryIAb controls the corn borer
RNA interference (RNAi):
- The nematode Meloidogyne incognita infects tobacco roots and reduces yield
- Nematode-specific genes are introduced into tobacco through Agrobacterium, so the plant makes both sense and antisense RNA
- These form double-stranded RNA that silences the matching mRNA of the nematode, so the parasite cannot survive
Golden rice:
- Engineered to make beta-carotene in the grain, which the body converts into vitamin A
- Aims to reduce vitamin A deficiency where diets depend heavily on rice
An everyday example. Bt cotton grown by farmers in Maharashtra and Gujarat needs fewer insecticide sprays against bollworms.
The substance. Bt toxin targets specific insects — it becomes active only in an alkaline insect gut with the right receptors.
Genetically modified crops can:
- Resist pests and reduce the use of chemical pesticides
- Tolerate drought, cold, salt and heat
- Reduce losses after harvest and carry better nutrition
Bt crops:
- The bacterium Bacillus thuringiensis makes crystal Bt toxin proteins
- The toxin is an inactive protoxin; in the alkaline gut of an insect it becomes active, binds the gut lining, creates pores and kills the insect
- The toxin genes are called cry genes — proteins coded by cryIAc and cryIIAb control cotton bollworms, and cryIAb controls the corn borer
RNA interference (RNAi):
- The nematode Meloidogyne incognita infects tobacco roots and reduces yield
- Nematode-specific genes are introduced into tobacco through Agrobacterium, so the plant makes both sense and antisense RNA
- These form double-stranded RNA that silences the matching mRNA of the nematode, so the parasite cannot survive
Golden rice:
- Engineered to make beta-carotene in the grain, which the body converts into vitamin A
- Aims to reduce vitamin A deficiency where diets depend heavily on rice
An everyday example. Bt cotton grown by farmers in Maharashtra and Gujarat needs fewer insecticide sprays against bollworms.
The substance. Bt toxin targets specific insects — it becomes active only in an alkaline insect gut with the right receptors.
How are human insulin, gene therapy and molecular diagnosis made possible by biotechnology?
Recombinant bacteria make human insulin, gene therapy corrects a faulty gene by supplying a working copy, and molecular techniques such as PCR, recombinant DNA probes and ELISA detect diseases early.
Human insulin:
- Insulin has two short polypeptide chains, A and B, joined by disulphide bridges
- In the body it is made as proinsulin, with an extra C peptide that is later removed
- DNA sequences for chains A and B are placed in plasmids of E. coli, which make the two chains separately
- The chains are extracted and combined through disulphide bonds to form human insulin
- Unlike insulin from animals, it does not cause allergic reactions in patients
Gene therapy:
- Corrects a gene defect by inserting a normal gene into a person's cells
- Example: adenosine deaminase (ADA) deficiency, which cripples the immune system
- Lymphocytes from the patient are grown in the laboratory, given a working ADA gene with a retroviral vector, and returned to the patient
- These cells do not live forever, so the treatment must be repeated; adding the gene to early embryonic cells could give a permanent cure
Molecular diagnosis:
- PCR detects tiny amounts of a pathogen's DNA, even before symptoms appear
- Recombinant DNA probes with radioactive labels find mutated genes by autoradiography
- ELISA detects antigens or antibodies, as in HIV testing
An everyday example. Diabetic patients across India inject recombinant human insulin made in bacteria and purified in bioreactors.
The substance. Early detection matters most — PCR can find a pathogen when its numbers are still too low to cause symptoms.
Human insulin:
- Insulin has two short polypeptide chains, A and B, joined by disulphide bridges
- In the body it is made as proinsulin, with an extra C peptide that is later removed
- DNA sequences for chains A and B are placed in plasmids of E. coli, which make the two chains separately
- The chains are extracted and combined through disulphide bonds to form human insulin
- Unlike insulin from animals, it does not cause allergic reactions in patients
Gene therapy:
- Corrects a gene defect by inserting a normal gene into a person's cells
- Example: adenosine deaminase (ADA) deficiency, which cripples the immune system
- Lymphocytes from the patient are grown in the laboratory, given a working ADA gene with a retroviral vector, and returned to the patient
- These cells do not live forever, so the treatment must be repeated; adding the gene to early embryonic cells could give a permanent cure
Molecular diagnosis:
- PCR detects tiny amounts of a pathogen's DNA, even before symptoms appear
- Recombinant DNA probes with radioactive labels find mutated genes by autoradiography
- ELISA detects antigens or antibodies, as in HIV testing
An everyday example. Diabetic patients across India inject recombinant human insulin made in bacteria and purified in bioreactors.
The substance. Early detection matters most — PCR can find a pathogen when its numbers are still too low to cause symptoms.
How are transgenic animals used, and what are biosafety, biopiracy and biopatents?
Transgenic animals carry and express a foreign gene and are used to study biology and disease, make medicines and test safety, while biosafety rules govern genetically modified organisms, biopatents protect inventions based on biological resources, and biopiracy is using such resources or traditional knowledge without permission or fair payment.
Uses of transgenic animals:
- Normal physiology and development — studying how genes regulate growth
- Study of disease — models for cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's disease
- Biological products — such as alpha-1-antitrypsin, used to treat emphysema
- Vaccine safety — testing vaccines, such as the polio vaccine, in transgenic mice
- Chemical safety testing — animals made more sensitive to toxic substances give faster results
Biosafety. Genetically modified organisms can behave unpredictably in ecosystems, so the Genetic Engineering Appraisal Committee (GEAC) of the Government of India assesses the safety of GM research and the release of GM organisms.
Biopatents. Patents granted for biological entities and products derived from them.
Biopiracy:
- Using the bio-resources or traditional knowledge of a country or community without authorisation or compensation
- Concerns have been raised over patent claims based on basmati rice, turmeric and neem, which draw on Indian traditional knowledge
- India has amended its patent laws to protect traditional knowledge and require benefit sharing
An everyday example. Neem-based pest sprays used by Indian farmers draw on traditional knowledge that anti-biopiracy rules aim to protect from unfair patents.
The substance. Most transgenic animals are mice — but transgenic rabbits, pigs, sheep, cows and fish have also been produced.
Uses of transgenic animals:
- Normal physiology and development — studying how genes regulate growth
- Study of disease — models for cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's disease
- Biological products — such as alpha-1-antitrypsin, used to treat emphysema
- Vaccine safety — testing vaccines, such as the polio vaccine, in transgenic mice
- Chemical safety testing — animals made more sensitive to toxic substances give faster results
Biosafety. Genetically modified organisms can behave unpredictably in ecosystems, so the Genetic Engineering Appraisal Committee (GEAC) of the Government of India assesses the safety of GM research and the release of GM organisms.
Biopatents. Patents granted for biological entities and products derived from them.
Biopiracy:
- Using the bio-resources or traditional knowledge of a country or community without authorisation or compensation
- Concerns have been raised over patent claims based on basmati rice, turmeric and neem, which draw on Indian traditional knowledge
- India has amended its patent laws to protect traditional knowledge and require benefit sharing
An everyday example. Neem-based pest sprays used by Indian farmers draw on traditional knowledge that anti-biopiracy rules aim to protect from unfair patents.
The substance. Most transgenic animals are mice — but transgenic rabbits, pigs, sheep, cows and fish have also been produced.
Exam tip
What earns full marks on biotechnology applications?
Explain the mechanism, not just the name — for Bt crops, say how the protoxin becomes active in the insect gut; for RNAi, say how double-stranded RNA silences the pest's mRNA.
- Bt cotton: cryIAc and cryIIAb against bollworms; Bt corn: cryIAb against the corn borer
- RNAi: Meloidogyne incognita in tobacco, delivered by Agrobacterium
- Insulin: chains A and B made separately and joined by disulphide bonds
- Gene therapy: ADA deficiency treated with a retroviral vector
The trap. Saying bacteria make insulin together with its C peptide. Chains A and B are made separately and joined; the C peptide is not part of the final product.
- Bt cotton: cryIAc and cryIIAb against bollworms; Bt corn: cryIAb against the corn borer
- RNAi: Meloidogyne incognita in tobacco, delivered by Agrobacterium
- Insulin: chains A and B made separately and joined by disulphide bonds
- Gene therapy: ADA deficiency treated with a retroviral vector
The trap. Saying bacteria make insulin together with its C peptide. Chains A and B are made separately and joined; the C peptide is not part of the final product.
Did you know
Why is golden rice yellow?
Ordinary white rice grains contain almost no beta-carotene, the orange-yellow pigment found in carrots and ripe mangoes.
In golden rice, genes for the pathway that makes beta-carotene have been added so that the pigment builds up in the grain itself, giving the rice its golden colour.
When people eat it, their bodies turn beta-carotene into vitamin A, which is needed for healthy vision — so the colour is the whole point of the project.
In golden rice, genes for the pathway that makes beta-carotene have been added so that the pigment builds up in the grain itself, giving the rice its golden colour.
When people eat it, their bodies turn beta-carotene into vitamin A, which is needed for healthy vision — so the colour is the whole point of the project.
Exam relevance
How does NEET test Bt crops, RNAi, insulin and gene therapy?
Biotechnology and its Applications is a recurring NEET chapter, and its questions test specific examples and mechanisms.
What gets asked. Cry genes and the pests they target, how Bt protoxin is activated, the parasite and host in RNAi, the structure of insulin and how recombinant insulin is made, ADA deficiency and gene therapy, uses of transgenic animals, and the role of GEAC.
Question types. Mostly statement-based and match-the-column questions, often pairing a gene or organism with its application.
Why it matters later. These examples build directly on the tools of Biotechnology: Principles and Processes — restriction enzymes, vectors and PCR.
The trap that costs marks. Thinking Bacillus thuringiensis is killed by its own toxin — the toxin stays as an inactive protoxin in the bacterium and becomes active only in the insect's alkaline gut.
What gets asked. Cry genes and the pests they target, how Bt protoxin is activated, the parasite and host in RNAi, the structure of insulin and how recombinant insulin is made, ADA deficiency and gene therapy, uses of transgenic animals, and the role of GEAC.
Question types. Mostly statement-based and match-the-column questions, often pairing a gene or organism with its application.
Why it matters later. These examples build directly on the tools of Biotechnology: Principles and Processes — restriction enzymes, vectors and PCR.
The trap that costs marks. Thinking Bacillus thuringiensis is killed by its own toxin — the toxin stays as an inactive protoxin in the bacterium and becomes active only in the insect's alkaline gut.
Key takeaways
What must you be able to do from this lesson?
- Agriculture: Bt crops with cry genes, RNAi against nematodes in tobacco, and golden rice rich in beta-carotene
- Medicine: recombinant human insulin, gene therapy for ADA deficiency, and molecular diagnosis by PCR, probes and ELISA
- Transgenic animals and ethics: uses of transgenic animals, biosafety through GEAC, biopatents and biopiracy
Why does Bt toxin kill a bollworm but not the bacterium that makes it?
- Medicine: recombinant human insulin, gene therapy for ADA deficiency, and molecular diagnosis by PCR, probes and ELISA
- Transgenic animals and ethics: uses of transgenic animals, biosafety through GEAC, biopatents and biopiracy
Why does Bt toxin kill a bollworm but not the bacterium that makes it?