Biotechnological Applications in Agriculture
Genetically Modified Organisms (GMOs)
- GMOs: Plants, bacteria, fungi, and animals whose genes have been altered by manipulation.
- First transgenic plant: Tobacco NEET 1999.
- First transgenic crop: Tobacco NEET 1999.
- Green Revolution: Tripled food supply via agrochemicals and better management, but insufficient for population growth and often too expensive for developing world farmers.
Advantages of Genetic Modification in Plants
- Made crops more tolerant to abiotic stresses (cold, drought, salt, heat) NEET 2020.
- Reduced reliance on chemical pesticides (pest-resistant crops) NEET 2020.
- Helped to reduce post-harvest losses (e.g., 'Flavr Savr' tomato) NEET 2020 2012.
- Increased efficiency of mineral usage by plants (prevents early exhaustion of soil fertility) NEET 2020.
- Enhanced nutritional value of food.
- Golden Rice: Transgenic variety of rice (derived from Basmati) enriched with Vitamin A to prevent night blindness NEET 2020 2015 2012 2010 2008 2006. It has yellow grains due to a gene introduced from a daffodil NEET 2019.
- Herbicide-resistant GM crops: Main objective is to reduce herbicide accumulation in food articles for health safety NEET 2008.
Pest Resistant Plants: Bt Cotton
- Bacillus thuringiensis (Bt): A bacterium widely used as a biological insecticide NEET 2009. Strains are used for designing novel bio-insecticidal plants NEET 2005.
- Target Insects: Lepidopterans (tobacco budworm, armyworm), Coleopterans (beetles), and Dipterans (flies, mosquitoes).
- Bt Cotton Characteristics: Provides high yield and resistance to bollworms NEET 2010. Grown widely by farmers in India NEET 2013. Also, GM Brinjal is developed for insect resistance NEET 2010.
Mechanism of Bt Toxin Action
Crucial Details & NEET PYQs
- Protoxin Formation: B. thuringiensis produces protein crystals containing toxic insecticidal protein (Cry endotoxins) NEET 2008. Exists as an inactive protoxin inside the bacteria NEET 2024 Re 2024 2009.
- Ingestion & Activation: Inactive protoxin is ingested by the insect and converted to an active toxin due to the alkaline pH of the insect gut NEET 2024 Re 2019 2015 2011 2010 2009 2006. Exception trap: It is NOT activated by acidic pH or stomach/body temp. Alkaline pH solubilizes the crystals NEET 2024 Re.
- Binding & Lysis: Activated toxin binds to the surface of midgut epithelial cells NEET 2024 Re 2011.
- Cell Death: Binding creates pores that cause cell swelling, lysis, and eventually insect death NEET 2024 Re 2024.
- cry Genes: The toxin is coded by a gene named cry. They are insect-group specific NEET 2024.
- cryIAc and cryIIAb control cotton bollworms NEET 2024 Re 2024.
- cryIAb controls corn borer NEET 2024 Re 2024.
Pest Resistant Plants: RNA Interference (RNAi)
- Pathogen: A nematode, Meloidogyne incognita, infects the roots of tobacco plants, reducing yield NEET 2016.
- RNA interference (RNAi): A method of cellular defense taking place in all eukaryotic organisms NEET 2024 Re 2020 2011.
- Mechanism: Involves the silencing of a specific mRNA due to a complementary double-stranded RNA (dsRNA) molecule that binds and prevents translation NEET 2019 2013. Crucial trap: It requires dsRNA, not ssRNA NEET 2024 Re.
- Source of complementary RNA: Viral infections (RNA genomes) or mobile genetic elements (transposons) that replicate via an RNA intermediate NEET 2022.
- Vector Used: Agrobacterium vectors are used to introduce nematode-specific genes into the host plant.
- Expression: DNA is introduced such that it produces both sense and anti-sense RNA in the host cells NEET 2012. These form dsRNA, initiating RNAi and silencing the nematode mRNA.
Biotechnological Applications in Medicine
Genetically Engineered Human Insulin (Humulin)
- First Human Hormone by rDNA: Insulin NEET 2014.
- Historical Source: Earlier extracted from the pancreas of slaughtered cattle and pigs. Caused allergic reactions in some patients NEET 2022.
- Insulin Structure: Mature insulin consists of two short polypeptide chains: Chain A and Chain B NEET 2023 2021.
- Linkage: Chains are linked together by disulphide bridges NEET 2023 2021 2020 2016. Exception trap: They are NOT linked by hydrogen or covalent bonds NEET 2020.
- Pro-hormone: In mammals, synthesized as a proinsulin containing an extra stretch called C peptide NEET 2023 2022 2021 2020.
- Maturation: C-peptide is not present in mature functional insulin; it is removed during maturation NEET 2023 2021 2020.
- Eli Lilly (1983): An American company prepared two DNA sequences for A and B chains, introduced them into plasmids of Escherichia coli to produce chains separately NEET 2024 Re 2022 2020 2008. Extracted and combined via disulphide bonds.
Gene Therapy
- Gene Therapy: Collection of methods allowing correction of a gene defect (via targeting and gene amplification) diagnosed in a child/embryo NEET 2021 2016.
- First Clinical Application: Given in 1990 to a 4-year-old girl with Adenosine Deaminase (ADA) deficiency NEET 2024 Re 2022 2016 2014 2012.
- ADA Function: Enzyme is crucial for the immune system. Deficiency results in Severe Combined Immunodeficiency (SCID) / dysfunction of the immune system NEET 2024 Re 2021.
- Standard non-curative treatments: Bone marrow transplantation or enzyme replacement therapy NEET 2024 Re 2009.
- Gene Therapy Mechanism:
- Lymphocytes from the patient's blood are grown in culture.
- A functional ADA cDNA is introduced into lymphocytes using a retroviral vector NEET 2022 2018.
- Cells are returned to the patient.
- Drawback: Requires periodic infusion of genetically engineered lymphocytes because the cells are not immortal NEET 2022 2009.
- Permanent Cure: Introducing the gene isolated from marrow cells producing ADA into cells at early embryonic stages NEET 2022 2009.
Molecular Diagnosis
- Limitation of Conventional Methods: Serum and urine analysis do not serve the purpose of early disease detection NEET 2023.
- PCR (Polymerase Chain Reaction): Used for amplification of nucleic acids to detect very low concentrations of pathogens (e.g., HIV in suspected AIDS patients) and detection of gene mutations in suspected cancer patients NEET 2021 2020.
- Sequence of PCR: Denaturation → Annealing → Extension NEET 2021.
- Exception trap: PCR is NOT used for the purification of isolated proteins NEET 2021.
- Autoradiography & Probe: A single-stranded DNA or RNA tagged with a radioactive molecule is called a probe NEET 2012 2010.
- Allowed to hybridize to complementary DNA in a clone of cells.
- Mutated gene detection: The mutated gene does not appear on the photographic film because the probe has no complementarity with it NEET 2021.
- ELISA (Enzyme Linked Immuno-Sorbent Assay): Based on the principle of antigen-antibody interaction NEET 2024 Re 2022. Key reagent is alkaline phosphatase or peroxidase NEET 2004 2003.
Transgenic Animals
Definition & Demographics
- Transgenic Animals: Animals with their DNA manipulated to possess and express an extra (foreign) gene in all their cells NEET 1995.
- Expression of transgene in target tissue is determined by the promoter NEET 2004.
- Over 95% of all existing transgenic animals are mice NEET 2011.
- First Cloned Animal: Dolly the sheep NEET 2000. Giant rat was formed by gene manipulation NEET 2000.
Applications of Transgenic Animals
- Study of Normal Physiology and Development: To study how genes are regulated and affect body functions (e.g., insulin-like growth factor).
- Study of Disease: Serve as models to investigate new treatments for human diseases (Cancer, Cystic fibrosis, Rheumatoid arthritis, Alzheimer's).
- Biological Products: Transgenic animals generate expensive human proteins. E.g., α-1-antitrypsin is used to treat emphysema NEET 2024 Re.
- First transgenic cow (Rosie, 1997): Produced human protein-enriched milk (2.4 grams per litre). Contained human α-lactalbumin, making it nutritionally more balanced for human babies than natural cow milk NEET 2022 Re 2011 2010.
- Vaccine Safety: Transgenic mice are used to test the safety of the polio vaccine before human use NEET 2010.
- Chemical Safety (Toxicity) Testing: Using animals carrying genes that make them highly sensitive to toxic substances to yield faster results.
Ethical Issues
Regulatory Bodies
- GEAC (Genetic Engineering Appraisal Committee): Set up by the Indian Government to make decisions regarding the validity of GM research and the safety of introducing GM-organisms for public services NEET 2024 Re 2018 2015.
Biopatency & Biopiracy
- Biopatent: A right granted by a government to an inventor to prevent commercial use of their invention. Not granted for complete natural genomes.
- The Basmati Rice Case (1997): An American company got patent rights on Basmati rice through the US Patent and Trademark Office. This "new" variety was actually derived from crossing Indian farmers' varieties with semi-dwarf varieties NEET 2018.
- Biopiracy: The term used to refer to the use of bio-resources by multinational companies and other organizations without proper authorization from the concerned country and its people, and without compensatory payment NEET 2024 Re 2020 2018.
- Bio-patenting Laws: The Indian Parliament cleared the second amendment of the Indian Patents Bill to prevent unauthorized exploitation of bio-resources and traditional knowledge NEET 2020.
Key Core Concepts & Extrapolations (Cross-Chapter PYQ Integrations)
- Totipotency: The capacity to generate a whole plant from any cell/explant NEET 2024.
- Somatic Hybridization: Fusing isolated protoplasts from two different varieties of plants NEET 2024.
- Agrobacterium tumefaciens: Delivers 'T-DNA' into plant cells. Its 'Ti' plasmid is modified to be non-pathogenic for gene transfer. Naturally, it transforms normal dicot plant cells into tumor cells NEET 2023 2004. Exception trap: It is NOT used for prokaryotic host cells NEET 2023.
- Pseudomonas putida: Genetically engineered microorganism successfully used in the bioremediation of oil spills NEET 2007.
- Hybridoma Technology: Hybrid cells resulting from myeloma (cancer) cells fused with B-cells, used to produce monoclonal antibodies NEET 1999.