Biotechnology and Its Applications Class 12 Notes

Scope of Biotechnology Applications

• Agriculture — Bt crops, GM crops, RNAi-mediated resistance.
• Medicine — recombinant insulin, gene therapy, molecular diagnostics.
• Research — transgenic animals for disease models and product testing.
• Ethics — patents, biopiracy, GEAC regulation in India.

Agricultural Applications — Bt Crops

• Bt toxin genes used: cryIAc and cryIIAb (cotton), cryIAb (corn), cryIAc (rice).
• Cry proteins (delta-endotoxins) exist as inactive protoxins in the bacterium; only in the alkaline gut of insects are they converted into the active toxin.
• The activated toxin binds to midgut epithelial cell receptors, creating pores that cause the insect to die.
• Because the protoxin is inactive in humans and livestock (no alkaline gut with matching receptors), Bt crops are considered safe for them.

GM Crops and RNAi-Mediated Pest Resistance

Genetically modified (GM) crops have had foreign genes inserted to improve yield, nutritional value and resistance to pests and drought. Up to 31% of India's crop area was under Bt cotton by 2014, boosting yield per hectare.

• Engineered DNA produces both sense and antisense RNA that pair into dsRNA.
• The dsRNA is processed into small interfering RNA (siRNA) by the host cell.
• siRNA targets and destroys the homologous mRNA of the invading nematode.
• Result: pest resistance without chemical sprays, showing RNAi specificity.

Medical Applications — Recombinant Human Insulin

The first genetically engineered pharmaceutical product for medical use was recombinant human insulin, produced in the late 1970s in the bacterium E. coli.

• E. coli was engineered to produce separate A and B chains, which were extracted, purified and combined by disulphide bonding into functional insulin.
• Producing the two chains separately avoids the need to chemically remove the C-peptide.
• The recombinant insulin made by Eli Lilly was the first such medicine; Humulin was introduced in 1982.
• It is identical to human insulin and avoids the allergic reactions of animal-derived insulin.

Gene Therapy

Classic example: treatment of Severe Combined Immuno-Deficiency (SCID) caused by a defect in the gene for the enzyme adenosine deaminase (ADA). The disease cripples the immune system because lymphocytes cannot function without ADA.

• Lymphocytes from the patient are collected and grown in culture.
• The functional ADA gene is introduced into these cells using a retrovirus as the vector (the viral genome is integrated into the host chromosome).
• Engineered cells are returned to the patient using a bioreactor — this is the ex vivo approach.
• A later, safer approach inserted the ADA gene into cells at the early embryonic stage so functional enzyme is produced the child's entire life.

Molecular Diagnostics and Transgenic Animals

• Polymerase Chain Reaction (PCR) — amplifies a tiny amount of DNA, even from a single cell, to detect a pathogen's genetic material.
• ELISA (Enzyme Linked Immuno-Sorbent Assay) — detects antigens or antibodies using enzyme-linked reactions.
• Recombinant DNA probes — single-stranded DNA with a radio-labelled or other marker that hybridises (binds) only to complementary sequences, revealing the presence of a specific gene or pathogen.

Example: Rosie, the first transgenic cow, produced human protein alpha-lactalbumin in her milk — around 2.4 grams per litre, a nutritionally enriched milk more like human breast milk.

Ethical Issues and Bioethics

• Biopiracy cases: patenting the use of turmeric for wound healing, neem for pest control, and basmati rice lines — later challenged and many revoked.
• GEAC (Genetic Engineering Approval Committee) in India — the statutory body that approves research involving genetically engineered organisms and the use of GMOs for commercial purposes.
• International agreements aim to reward source countries and share benefits fairly with indigenous and farming communities.

Solved Examples

Example: Why does Bt toxin kill the insect but not the plant or livestock consuming the crop?

Solution: The cry gene codes for an inactive protoxin. It is activated to the toxic form only in the alkaline gut (high pH) of the insect, where it binds to specific midgut receptors and creates pores. Humans and cattle lack this alkaline gut with matching receptors, so the protoxin stays inactive and harmless for them.

Example: How was recombinant human insulin produced and why is mature insulin two chains?

Solution: Human insulin is first synthesised as proinsulin — a single chain with A and B regions linked by an extra C-peptide. E. coli was engineered to produce the A and B chains separately; they were extracted, purified and joined by disulphide bonds to form mature insulin. The C-peptide is absent in the final product because the two chains were made directly, avoiding the need to cleave it off.