Board exam focus — Biotechnology and its Applications (CBSE & HBSE)

CBSE focuses on Bt crops (cry genes, toxin mechanism), golden rice, recombinant insulin, gene therapy (ADA deficiency), molecular diagnostics (PCR, ELISA), transgenic animals, and ethical issues (biopiracy, GEAC). HBSE emphasises definitions, Bt cotton, recombinant insulin, gene therapy, and biosafety.

Genetically Modified Crops and Agricultural Biotechnology

Genetically Modified Organisms (GMOs)

A genetically modified organism (GMO) is an organism whose genome has been altered by the insertion of one or more genes from another organism (or synthetic genes) using genetic engineering techniques. GM plants are also called transgenic plants.

Benefits of GM crops:

• Higher crop yields, resistance to pests and diseases
• Tolerance to abiotic stresses (drought, salinity, cold, flooding)
• Enhanced nutritional quality (biofortification)
• Production of pharmaceuticals in plant tissues (molecular farming)
• Reduced dependence on chemical pesticides and herbicides

Bt Crops

Bacillus thuringiensis (Bt) produces crystal proteins (Cry proteins / delta-endotoxins) that are toxic specifically to certain insect larvae. The cry genes encoding these proteins have been transferred to crop plants to make them pest-resistant.

Mechanism of Bt toxin action:

1. Bt crystal proteins (protoxins) are produced in crystalline form in bacterial spores
2. In the highly alkaline gut (pH 9-10) of susceptible insect larvae, the crystals are solubilised
3. Solubilised protoxin is cleaved by gut proteases → active toxin fragment
4. Active toxin binds specific glycoprotein receptors (cadherins, aminopeptidase N) on midgut epithelial brush border membrane
5. Toxin inserts into membrane → pore formation → osmotic imbalance → cell lysis
6. Insect stops feeding and dies within 1-3 days
7. Species-specificity: receptor types differ between insect species; no receptors in mammals → safe

Bt Cotton (Most important example in India):

• Bollworm complex (pink bollworm, American bollworm, spotted bollworm) is the most devastating pest of cotton
• cry1Ac gene (from B. thuringiensis var. kurstaki): effective against American bollworm (Helicoverpa armigera)
• cry2Ab gene: additional protection against bollworms
• Bollgard I (Monsanto/MAHYCO): contains cry1Ac gene; approved in India 2002
• Bollgard II: contains cry1Ac + cry2Ab genes; better spectrum
• Result: dramatically reduced insecticide use on cotton (from 50-60% of all insecticide use to much less); reduced farmer costs; increased yields
• Controversy: cost of seeds; development of resistance; effect on biodiversity

Bt Brinjal (Bt Eggplant):

• cry1Ac gene against fruit and shoot borer (Leucinodes orbonalis)
• Approved in Bangladesh (2013); moratorium in India (2010 — pending further study)

Other Pest-resistant Crops: RNAi (RNA interference) for nematode control:

• Parasitic nematode Meloidogyne incognita attacks roots of tobacco
• Strategy: introduce dsRNA complementary to specific nematode genes (e.g., 16D10 gene involved in nematode parasitism)
• dsRNA triggers RNAi in nematode → specific mRNA degraded → gene silenced → nematode unable to parasitise plant

Herbicide Tolerance:

• Roundup Ready crops (glyphosate tolerance): gene for glyphosate-insensitive EPSPS enzyme from Agrobacterium tumefaciens introduced into soybean, maize, canola, cotton
• Farmers spray glyphosate (Roundup) → kills weeds but not crop

Golden Rice — Biofortification

Problem: Vitamin A Deficiency (VAD) affects ~250 million people globally, especially children in developing countries. Causes blindness (250,000-500,000 children/year), increased susceptibility to infections, and death.

Solution: Golden Rice — rice engineered to produce beta-carotene (provitamin A) in the endosperm.

Development (1999-2000):

• Ingo Potrykus (ETH Zurich) and Peter Beyer (University of Freiburg)
• Wild-type rice endosperm: produces no beta-carotene (lacks phytoene synthase and lycopene beta-cyclase)
• Genes introduced into rice:
• psy (phytoene synthase, from daffodil Narcissus pseudonarcissus) → converts GGPP to phytoene
• crtI (phytoene desaturase, from bacterium Erwinia uredovora) → converts phytoene through lycopene → beta-carotene
• Later, psy from maize was used in Golden Rice 2 (2004) — 23x more beta-carotene

Significance: addresses micronutrient deficiency in rice-eating populations. Controversy: Golden Rice has faced opposition from anti-GMO groups despite safety approvals in several countries.

Other Biofortification Examples:

• Iron-rich beans: 3x higher iron content through breeding + genetic engineering
• Protein-rich QPM (Quality Protein Maize): increased lysine and tryptophan
• High-beta-carotene sweet potato: breeding and genetic engineering
• Zinc-enriched wheat: breeding

Medical Applications of Biotechnology

Recombinant Proteins in Medicine

Biotechnology has enabled the large-scale production of therapeutic proteins using recombinant DNA technology.

Recombinant Human Insulin (Humulin)

Historical context: Before 1982, diabetic patients used insulin extracted from pig (porcine) or cow (bovine) pancreas. This caused immune reactions in some patients and was limited in supply.

Structure of insulin: Human insulin (51 amino acids) consists of two polypeptide chains: Chain A (21 aa) and Chain B (30 aa) linked by two inter-chain and one intra-chain disulfide bridges. It is synthesised as preproinsulin → proinsulin (A+B chains + connecting C peptide) → mature insulin (C peptide removed by proteolytic cleavage in Golgi/secretory vesicles).

Production of recombinant insulin (Eli Lilly, 1982): Method 1 (Early method — separate chains):

1. Synthesise cDNA for insulin A chain and insulin B chain separately
2. Clone each cDNA into separate expression vectors, fused to beta-galactosidase gene (for expression in E. coli)
3. Transform E. coli; induce expression → beta-galactosidase-insulin fusion proteins produced in inclusion bodies
4. Extract chains; treat with CNBr (cyanogen bromide) to cleave the two fusion proteins at Met residue → release A and B chains
5. Mix purified A and B chains under appropriate conditions → disulfide bonds form → active recombinant insulin

Method 2 (Current method — proinsulin):

1. Clone human proinsulin gene (A + C + B chain sequence) into expression vector
2. Express in E. coli or yeast (Saccharomyces cerevisiae — preferred for proper folding and disulfide bond formation)
3. Proinsulin folds with correct disulfide bonds
4. C peptide removed enzymatically → mature insulin identical to human insulin
5. Purify by affinity chromatography and other steps

Advantages over animal insulin: identical to human insulin → no immune reactions; large-scale, consistent supply; reduced cost.

Recombinant Growth Hormone (rGH / Somatropin):

• Produced in E. coli; used for treatment of growth hormone deficiency and Turner syndrome
• Previously extracted from cadaver pituitary glands → risk of Creutzfeldt-Jakob disease (prion contamination) — now replaced by recombinant GH

Recombinant Clotting Factors:

• Factor VIII (for Haemophilia A) and Factor IX (for Haemophilia B): previously extracted from human blood → risk of HIV and hepatitis contamination; now produced in CHO cells using recombinant technology
• Produced also in transgenic cattle milk (pharming)

Recombinant Erythropoietin (EPO):

• Produced by CHO cells; used to treat anaemia associated with chronic kidney disease and chemotherapy

Gene Therapy

Gene therapy is the correction of a genetic disorder by introducing a functional copy of the defective gene into the patient's cells.

ADA Deficiency (Adenosine Deaminase Deficiency) — First Human Gene Therapy (1990):

Background: Adenosine deaminase (ADA) is an enzyme involved in purine metabolism. Deficiency causes accumulation of toxic deoxyadenosine → selective killing of T and B lymphocytes → Severe Combined Immunodeficiency (SCID). Children with SCID lack functional immune systems (the "bubble boy" disease — must live in sterile conditions).

Gene therapy procedure:

1. Lymphocytes collected from patient (from blood)
2. Cultured in vitro
3. Functional ADA cDNA (under a strong promoter) inserted into retroviral vector (retrovirus integrates into host genome)
4. Retroviral vector used to infect patient's lymphocytes in culture
5. Engineered lymphocytes (now expressing ADA) reinfused into patient's bloodstream
6. Lymphocytes populate lymphoid organs → produce ADA → immune function improved

Limitations: Treatment is not permanent — lymphocytes have a limited lifespan; new cells produced from stem cells in bone marrow will still lack ADA. Must be repeated periodically. Permanent cure requires gene therapy on bone marrow stem cells (hematopoietic stem cell gene therapy).

Current approaches: HSC (hematopoietic stem cell) gene therapy with retroviruses or lentiviruses; gene editing with CRISPR-Cas9 for precise correction.

Other gene therapies:

• Haemophilia: Factor VIII or IX gene delivery to liver
• Cystic fibrosis: CFTR gene to lung epithelium (difficult due to barrier)
• Leber's congenital amaurosis (retinal dystrophy): AAV delivery to retinal cells (FDA approved)
• Spinal muscular atrophy (SMA): Zolgensma (AAV9-SMN1) — most expensive drug ever

Delivery systems (vectors) for gene therapy:

• Viral: retroviruses (integrate stably but random insertion can activate oncogenes), lentiviruses, AAV (adeno-associated virus — non-integrating; low immunogenicity), adenoviruses
• Non-viral: liposomes, nanoparticles, naked DNA

Molecular Diagnostics

ELISA (Enzyme-Linked Immunosorbent Assay): Detects antigens or antibodies in patient samples using enzyme-linked antibodies.

• Direct ELISA: antigen in sample captured by antibody on plate; detected by enzyme-conjugated secondary antibody + substrate → colour change
• Sandwich ELISA: uses two antibodies (capture + detection)
• Indirect ELISA: detects antibodies in patient serum
• Applications: HIV diagnosis (detects anti-HIV antibodies), hepatitis B, allergy testing, pregnancy tests (hCG), drug testing

PCR for Diagnostics:

• Detects very low quantities of pathogen DNA/RNA (a few molecules sufficient)
• HIV: PCR can detect HIV RNA within days of infection (before antibodies appear — window period)
• Drug-resistant tuberculosis: PCR identifies rifampicin-resistant mutations in rpoB gene (GeneXpert)
• Viral infections: COVID-19 (RT-PCR), influenza, dengue
• Prenatal diagnosis: detect sickle cell anaemia, cystic fibrosis, Down syndrome from foetal DNA (amniocentesis, CVS)

DNA Fingerprinting (DNA Profiling):

• Based on VNTR (Variable Number Tandem Repeats) or STR (Short Tandem Repeats) analysis
• Individual-specific pattern
• Applications: forensics (criminal investigation), paternity testing, population genetics, disaster victim identification
• Technique: DNA extracted → PCR amplification of VNTR/STR loci → gel electrophoresis → unique banding pattern per individual

Transgenic Animals and Ethical Issues

Transgenic Animals

Transgenic animals are animals that have had a foreign gene (transgene) stably integrated into their genome in every cell.

Methods of creating transgenic animals:

• Pronuclear microinjection: inject DNA into male pronucleus of fertilised egg
• Retroviral vectors: infect early embryos
• ES cell targeting: introduce gene into embryonic stem cells → chimeric animal → breed to germline

Examples of transgenic animals and their applications:

1. Rosie Cow (Edinburgh, 1997):

• Human alpha-lactalbumin gene inserted into cow genome
• Rosie's milk contains human alpha-lactalbumin (at 2.4 g/L)
• More balanced nutritional composition than normal cow milk, suitable for human babies
• Demonstrates pharming concept

2. Pharming (Pharmaceutical farming): Using transgenic animals to produce biopharmaceuticals in their milk, blood, or urine.

• Factor VIII (for haemophilia A): produced in milk of transgenic sheep (Polly, 1997) and pigs
• Factor IX (for haemophilia B): transgenic sheep milk
• alpha-1-antitrypsin (for emphysema, alpha-1-antitrypsin deficiency): transgenic sheep (Tracy) milk; early commercial pharming product
• Tissue plasminogen activator (tPA): produced in goat milk (GTC Biotherapeutics)
• Advantages: large volumes of purified protein in milk; natural folding and glycosylation; scalable

3. Oncomouse (Harvard Mouse, 1988):

• First patented transgenic animal
• Contains activated human c-Ha-ras oncogene (driven by MMTV promoter)
• Highly susceptible to mammary cancer → used in cancer research; testing anti-cancer drugs
• Created by Philip Leder and Timothy Stewart (Harvard)

4. Knock-out (KO) and Knock-in (KI) mice:

• KO mice: specific gene inactivated (knocked out) by homologous recombination in ES cells
• Used to determine gene function; create disease models (CFTR knockout = cystic fibrosis model)
• More precise than transgenic; KI inserts specific mutation

5. Transgenic animals as disease models:

• Huntington's disease mouse: CAG repeat expansion in Huntingtin gene
• Alzheimer's mouse: human APP (amyloid precursor protein) + presenilin genes
• Diabetes mouse (NOD mice, STZ-treated, db/db mice)
• Used in drug development and testing

6. Xenotransplantation (future):

• Transgenic pigs with human complement regulatory proteins (hDAF) to prevent hyperacute rejection
• Knock-out of alpha-1,3-galactosyltransferase in pig to eliminate xenoantigen
• CRISPR-edited pigs (George Church lab) with 62 porcine ERV retrovirus sequences removed

Ethical Issues in Biotechnology

GEAC (Genetic Engineering Appraisal Committee):

• Apex body in India under Ministry of Environment, Forest and Climate Change
• Responsible for approving genetically modified organisms (GMOs) for environmental release and commercial use
• Reviews safety data on GM crops, food, and other GMOs
• Controversies: delayed approval process vs. industry pressure; anti-GMO advocacy vs. scientific consensus

Biosafety Concerns:

1. Gene flow: transgenes may spread from GM crops to wild relatives via pollen → create superweeds or disrupt ecosystems
2. Non-target effects: Bt toxins might harm non-target insects (Monarch butterfly controversy — later studies showed minimal real-world risk at field concentrations)
3. Antibiotic resistance marker genes: marker genes used in transformation could potentially transfer to gut microbiota
4. Allergenicity: novel proteins might be allergenic (Brazil nut gene in soybean caused IgE reactions in Brazil nut-sensitive individuals → product withdrawn)
5. Biodiversity: widespread adoption of few GM varieties may reduce agricultural biodiversity (genetic erosion)

Biopiracy: Exploitation of biological resources and traditional knowledge of communities/countries without sharing benefits equitably.

Examples:

• **Neem (Azadirachta indica):** W.R. Grace Co. patented use of Azadirachtin (neem extract) as pesticide in USA and Europe — overturned after challenge by India and European groups (EPO, 2000)
• **Turmeric (Curcuma longa):** US patent (1995) granted for wound healing with turmeric — challenged and revoked by India (turmeric use documented in ancient Indian texts)
• Basmati rice: RiceTec Inc. (USA) patented certain Basmati rice varieties — India challenged successfully; most claims withdrawn
• Bitter gourd, mustard, taro, jaljeera — other examples of Indian traditional knowledge claimed in patents

CBD (Convention on Biological Diversity, 1992): International treaty requiring equitable sharing of benefits from biodiversity resources between countries that provide genetic resources and companies/individuals that use them. India enacted the Biological Diversity Act 2002 to implement CBD.

TRIPs (Trade-Related Intellectual Property Rights) agreement: TRIPS requires WTO member countries to grant patents on genetically modified organisms and processes. Conflict with developing countries' interests.

Ethical issues in human biotechnology:

• Germ-line gene editing: CRISPR editing of human embryos (He Jiankui case, 2018 — CCR5 editing → widely condemned)
• Designer babies: selection of traits in embryos (preimplantation genetic diagnosis vs genetic enhancement)
• Genetic discrimination: use of genetic information in insurance, employment
• Privacy of genetic data

Frequently asked questions

Are these Biotechnology and its Applications notes free?

Yes — the Biotechnology and its Applications notes for Biology (Class 12) on Siksha Sarovar are completely free to read, with no account required.

Do these notes follow CBSE and HBSE?

Yes. The Biotechnology and its Applications notes are NCERT-aligned and include guidance for both CBSE and Haryana Board (HBSE), with important questions and MCQs for revision.

What does the Biotechnology and its Applications chapter cover?

Concept explanations, key formulas and definitions, fully solved examples and board-pattern practice questions for Biotechnology and its Applications.