Biotechnology has moved from the laboratory into everyday life, revolutionising medicine, agriculture, and industry. NCERT Class 12 Chapter 10 focuses on three major application areas: biotechnological applications in medicine, in agriculture, and the ethical/social issues surrounding genetically modified organisms (GMOs).
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Biotechnological Applications in Medicine
1. Recombinant Proteins / Therapeutics
Before recombinant DNA technology, insulin for diabetics was extracted from pigs and cattle — slightly different from human insulin, causing allergic reactions. In 1982, Eli Lilly produced the first recombinant human insulin (Humulin) by inserting human insulin genes into E. coli.
Human insulin consists of two polypeptide chains: Chain A (21 amino acids) and Chain B (30 amino acids). These are produced separately in E. coli (as fusion proteins with beta-galactosidase), extracted, purified, and joined by disulfide bonds to form active insulin.
- Other important recombinant therapeutics:
- Human Growth Hormone (hGH): produced in E. coli; treats dwarfism
- Erythropoietin: stimulates RBC production; treats anaemia in kidney disease patients
- Streptokinase: produced by Streptococcus, modified recombinantly; dissolves blood clots (thrombolytic agent)
- Interferon: antiviral proteins produced recombinantly; treat viral infections and certain cancers
- Factor VIII: clotting factor for haemophilia A
2. Gene Therapy
Gene therapy involves inserting a correct or therapeutic gene into the cells of a patient with a genetic defect to replace or supplement a faulty gene.
- ADA Deficiency (Adenosine Deaminase Deficiency):
- ADA enzyme is essential for immune system function. Deficiency causes Severe Combined Immunodeficiency (SCID) — the child lives in a bubble and is susceptible to every infection.
- First clinical gene therapy trial: 1990
- Approach: Lymphocytes are taken from the patient, the ADA gene is introduced via a retroviral vector, and the corrected cells are returned to the patient.
- Limitation: Not permanent — lymphocytes have a short life span, so treatment must be repeated. A more permanent solution is to introduce the gene into embryonic stem cells.
- Vectors for Gene Therapy:
- Retroviruses (integrate into host genome)
- Adenoviruses (do not integrate; may trigger immune response)
- Adeno-associated viruses (AAV) — preferred as they are non-pathogenic
3. Molecular Diagnosis
Traditional diagnostics detect symptoms after disease develops. Molecular techniques detect diseases earlier and with much greater precision.
- PCR (Polymerase Chain Reaction): amplifies pathogen DNA/RNA from even tiny samples; used in HIV detection, TB, COVID-19. One copy of viral or bacterial DNA can be detected.
- ELISA (Enzyme-Linked Immunosorbent Assay): based on antigen-antibody interaction. Used to detect HIV antibodies, pregnancy hormones (hCG), and other proteins in blood/urine. A positive test causes colour change via an enzyme-linked antibody.
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Biotechnological Applications in Agriculture
Transgenic Plants (GM Crops)
- Bt Crops:
- Bt cotton: The gene for Bt toxin (cry genes) from Bacillus thuringiensis is introduced into cotton plants. The Cry proteins are produced in the plant and kill bollworm larvae when they eat the plant. CryIAc and CryIIAb control cotton bollworm; CryIAb controls corn borer.
- The toxin is expressed as a pro-toxin in bacteria; it is only activated in the alkaline midgut of insects.
- Bt brinjal (Bt eggplant): introduced cry genes to confer resistance to shoot and fruit borer.
- RNA Interference (RNAi) / Gene Silencing:
- A post-transcriptional silencing technique using double-stranded RNA (dsRNA) that triggers destruction of the corresponding mRNA.
- Application: Tobacco mosaic virus resistance, Meloidogyne (nematode) resistance — nematodes that parasitise plant roots.
- Using Agrobacterium as a vector, specific dsRNA for nematode genes is introduced into host plant cells; when the nematode eats the plant cells, the dsRNA silences essential nematode genes, killing it.
- Golden Rice:
- Transgenic rice enriched with beta-carotene (provitamin A) — to address vitamin A deficiency.
- Beta-carotene biosynthesis genes from daffodil (Narcissus pseudonarcissus) and a bacterial gene were introduced into rice endosperm.
- Vitamin A deficiency causes blindness (xerophthalmia) in millions of children in developing countries.
- Pest-Resistant and Herbicide-Tolerant Crops:
- Herbicide tolerance: introduction of specific genes to detoxify herbicides (e.g., glyphosate-tolerant "Roundup Ready" crops).
- Delay of fruit ripening: antisense RNA technology used in tomatoes (Flavr Savr tomato).
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Ethical Issues and Biopiracy
- GMO Safety Concerns:
- Potential transfer of antibiotic resistance genes to gut bacteria
- Possibility of transgenic crop genes escaping into wild relatives (gene pollution)
- Toxicity to non-target organisms
- Long-term health effects on humans
- Biopiracy:
- The unauthorised exploitation of biological resources, traditional knowledge, or biodiversity of indigenous communities by corporations or researchers without proper compensation.
- Examples: Basmati rice (India), Turmeric (India), Neem — patents taken by foreign companies on traditional Indian uses.
- India and other countries have enacted legislation (Biological Diversity Act, 2002) to protect bio-resources and traditional knowledge.
- Ethical Debates:
- Genetically Modified Organisms raise ethical concerns about "playing God"
- Safety, labelling, and consumer choice debates
- GEAC (Genetic Engineering Approval Committee) in India regulates GMO approval for commercial release.
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Why was recombinant human insulin superior to animal insulin for diabetic patients?
Recombinant human insulin has the exact same amino acid sequence as natural human insulin, unlike pig or cattle insulin which differ slightly. This eliminates allergic reactions and immune responses common with animal insulins.
How is the Bt toxin made safe for humans but toxic to insects?
Bt toxin exists as an inactive pro-toxin protein crystal. In the alkaline midgut of susceptible insects, the pro-toxin is solubilised and activated by proteases. It binds to midgut epithelial receptors, creates pores, and kills the insect. Human stomachs are acidic — the pro-toxin is not activated, making it safe for humans.
A patient with ADA deficiency receives gene therapy. Why must the treatment be repeated periodically?
The ADA gene is introduced into the patient's own T-lymphocytes (white blood cells). Lymphocytes are short-lived and are replaced by new cells from bone marrow. New cells do not carry the corrected gene. Therefore, gene therapy must be repeated. A permanent cure would require correcting haematopoietic stem cells (which give rise to all blood cells).
How does RNAi protect plants from nematode infection?
The nematode-specific dsRNA introduced into the plant (via Agrobacterium) is taken up by the nematode as it feeds on plant cells. Inside the nematode, the dsRNA triggers the RNAi pathway: it is processed into small interfering RNA (siRNA) that silences specific essential nematode genes, killing the nematode.
Explain the principle of ELISA used in HIV diagnosis.
ELISA is based on antigen-antibody reactions. HIV infection causes the host to produce anti-HIV antibodies. In ELISA, patient serum is added to wells coated with HIV antigens. Anti-HIV antibodies (if present) bind to the antigen. A secondary enzyme-linked antibody binds to the primary antibody. A substrate is added — the enzyme converts it to a coloured product. Colour development = HIV positive.
What is the significance of Golden Rice, and what genes were introduced?
Golden Rice was engineered to produce beta-carotene (provitamin A) in the rice endosperm. Genes inserted: phytoene synthase gene from daffodil and the crt1 gene from the bacterium Erwinia uredovora. The rice appears golden due to the yellow beta-carotene pigment. It aims to combat vitamin A deficiency causing childhood blindness.
What is biopiracy? Give one example from India.
Biopiracy is the exploitation of biological resources and traditional knowledge of indigenous communities by external parties (typically corporations) without proper authorisation, benefit-sharing, or acknowledgment. Example: A US company (W. R. Grace) obtained patents on the use of neem tree extracts as a pesticide and fungicide — knowledge that Indian farmers had used for centuries. India successfully challenged and revoked several such patents.
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Summary
- Human insulin: Chain A + Chain B, joined by disulfide bonds; produced in E. coli
- GEAC: Genetic Engineering Approval Committee (India) — approves GMOs for release
- cry genes: encode Bt toxin; cry1Ac, cry1Ab, cry2Ab — different specificities
- RNAi triggers: double-stranded RNA (dsRNA) → siRNA → mRNA degradation
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Common mistakes
Students often confuse ELISA (detects antigens/antibodies) with PCR (detects nucleic acids). Remember Bt cotton has a bacterial gene (not a human gene). Biopiracy involves taking without compensation — it is not the same as normal scientific research using natural resources. Golden Rice addresses vitamin A deficiency (not iron or protein deficiency).
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Summary
Biotechnology applications span medicine (recombinant insulin, gene therapy, molecular diagnostics) and agriculture (Bt crops, Golden Rice, RNAi-based resistance). However, they also raise ethical concerns about GMO safety, ecological impact, and biopiracy. Regulatory bodies like GEAC and laws like India's Biological Diversity Act help govern these technologies responsibly.