Biotechnology And Its Applications Class 12 Revision Notes

Biotechnology Applications in Agriculture & Pest Resistance

Biotechnology has revolutionized agriculture through the development of Genetically Modified Organisms (GMOs). Instead of relying on chemical pesticides and fertilizers, which harm the environment and incur high costs, pest-resistant crops and abiotic stress-tolerant crops have been engineered. The classic exam example is Bt Cotton, developed by incorporating genes from the soil bacterium Bacillus thuringiensis. The bacterium produces a crystalline protein (Cry protein) which exists as an inactive protoxin. When ingested by targeted insect pests (such as lepidopterans, coleopterans, and dipterans), the alkaline pH of the insect's gut solubilizes these crystals, converting the protoxin into its active form. This active toxin binds to the surface of midgut epithelial cells, creating pores that cause cell swelling, lysis, and ultimately, the death of the pest. Another breakthrough is RNA Interference (RNAi), a cellular defense mechanism used to protect plants like tobacco from the nematode Meloidogyne incognita.

Important Biological Terms to Remember

Biopiracy

The unauthorized commercial exploitation of bioresources and traditional knowledge of a nation by multinational corporations without proper authorization or fair compensation.

Gene Therapy

A collection of methods that allows the correction of a gene defect diagnosed in a child or embryo by delivering functional normal genes into cells to replace non-functional ones.

RNA Interference (RNAi)

A eukaryotic cellular defense mechanism where double-stranded RNA (dsRNA) inhibits gene expression by neutralizing targeted complementary mRNA molecules.

Transgenic Animals

Animals whose genomes have been deliberately modified by inserting a foreign gene to express specific, useful traits or products.

Humulin

The trade name for genetically engineered human insulin synthesized by combining separately produced polypeptide chains A and B using disulfide bonds in vitro.

Cry Proteins

Crystalline insecticidal proteins encoded by the cry genes of Bacillus thuringiensis that selectively kill specific orders of insect pests.

Step-by-Step Mechanism of RNA Interference (RNAi)

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Natural Pro-insulin vs. Genetically Engineered Insulin (Humulin)

Must Remember: Key Applications & Ethics

• Critical research areas of biotechnology include providing the best catalyst, creating optimal conditions, and downstream processing.
• Bacillus thuringiensis produces Cry proteins; cryIAc and cryIIAb control cotton bollworms, while cryIAb controls corn borer.
• In gene therapy, the first clinical trial was performed in 1990 on a 4-year-old girl with Adenosine Deaminase (ADA) deficiency.
• ADA deficiency can be cured permanently if functional ADA-producing marrow cells are introduced at early embryonic stages.
• Transgenic cow 'Rosie' (1997) produced human protein-enriched milk containing human alpha-lactalbumin (2.4 grams per liter).
• 95 percent of all existing transgenic animals are transgenic mice, primarily used for safety testing of vaccines.
• GEAC (Genetic Engineering Appraisal Committee) is the Indian statutory body that decides the safety of introducing GMOs for public services.
• Over 200,000 varieties of rice exist in India alone, making its bioresources highly vulnerable to biopiracy.

Key Examples of Biotech Applications

• Bt Cotton: Transgenic cotton plants containing insecticidal genes from Bacillus thuringiensis that offer direct resistance to cotton bollworms without external pesticides.
• ADA Deficiency Cure: A retroviral vector is used to introduce functional ADA cDNA into the patient's cultured T-lymphocytes, which are then infused back into the patient.
• Molecular Farming (Rosie the Cow): Producing human-alpha-lactalbumin in transgenic cow milk to make it more nutritionally balanced for human infants than natural cow milk.

Common Board Traps and Marking Cues

Board Trap Alert: Students often confuse the pH condition for Bt toxin activation. Remember, the protoxin is inactive inside the Bacillus bacterium because of the neutral/acidic cellular conditions, but becomes active inside the insect gut due to the alkaline pH. Additionally, in genetically engineered insulin, emphasize that the C-peptide is absent in mature functional insulin. Do not write that Escherichia coli produces mature insulin directly; chains A and B are produced separately and joined later via disulfide bonds in vitro.

Practice Questions with Solutions

• Why does Bt toxin not kill the Bacillus bacterium itself? The Bt toxin is produced as an inactive protoxin within the bacterium. It only gets converted into its active toxic form in the alkaline pH environment of an insect's gut.
• What is the primary function of the C-peptide in pro-insulin? The C-peptide links chains A and B in pro-insulin. It is non-functional for glucose regulation and must be cleaved out for the insulin molecule to mature into its active form.
• Name the nematode that infects tobacco roots and explain how its infestation is prevented. Meloidogyne incognita. Its infestation is prevented using RNA interference (RNAi), which silences the parasite's essential mRNA inside host tobacco cells.
• What is the role of GEAC in biotechnology? The Genetic Engineering Appraisal Committee (GEAC) evaluates the safety of introducing genetically modified organisms (GMOs) and regulates experimental field trials for public use.

Frequently Asked Questions