Biotechnology and its Applications
Biotechnology applications span agriculture, medicine, transgenic animals and raise ethical questions. Organisms whose genes have been altered by manipulation are Genetically Modified Organisms (GMO).
Agriculture
- GM benefits: tolerance to abiotic stresses (cold, drought, salt, heat); pest resistance (reduced pesticide use); reduced post-harvest losses; better mineral-use efficiency; enhanced nutrition (golden rice = Vitamin A enriched).
- Bt cotton: Bt toxin is produced by Bacillus thuringiensis. It forms protein crystals containing a toxic protein. The toxin exists as an inactive protoxin in the bacterium; once ingested by an insect, the alkaline pH of the gut solubilises the crystal and activates it. The active toxin binds midgut epithelial cells, creating pores -> swelling, lysis and death.
- cry genes: code the toxin. cryIAc and cryIIAb control cotton bollworms; cryIAb controls corn borer. Choice depends on crop and target pest (insect-group specific).
- Pest-resistant plants via RNAi: the nematode Meloidogyne incognitia infects tobacco roots. Using Agrobacterium vectors, nematode-specific genes producing sense + anti-sense RNA were introduced; the complementary RNAs form dsRNA that triggers RNA interference (RNAi), silencing the nematode's mRNA so the parasite cannot survive.
Medicine
- Genetically engineered insulin (humulin): insulin has two chains, A and B, joined by disulphide bridges. It is made as a pro-hormone with an extra C peptide that is removed during maturation. In 1983 Eli Lilly made the A and B chain DNA in E. coli plasmids, produced the chains separately, and combined them by disulfide bonds. Recombinant insulin is identical to human insulin and avoids allergy.
- Gene therapy: inserts genes into a person's cells/tissues to correct a defect. First clinical gene therapy (1990) treated a 4-year-old girl with ADA (adenosine deaminase) deficiency (gene deletion). Functional ADA cDNA is introduced into the patient's lymphocytes via a retroviral vector; since these are not immortal, periodic infusion is needed. Embryonic-stage correction could be permanent.
- Molecular diagnosis: PCR amplifies low amounts of pathogen nucleic acid for early detection (e.g., HIV in AIDS, cancer mutations). Radioactive probes hybridise to complementary DNA, detected by autoradiography (mutated gene clone does not appear). ELISA is based on antigen-antibody interaction.
Transgenic animals
- Animals with an extra foreign gene; over 95% are mice. Uses: study normal physiology/development (e.g., insulin-like growth factor); study disease (models for cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's); make biological products (Rosie, 1997, gave milk with human alpha-lactalbumin; alpha-1-antitrypsin treats emphysema); vaccine safety (transgenic mice test polio vaccine); chemical (toxicity) safety testing.
Ethical issues
- GM organisms can have unpredictable ecological effects, so GEAC (Genetic Engineering Approval Committee) judges the validity of GM research and safety of releasing GMOs.
- Biopiracy: use of bio-resources by companies/organisations without authorisation or compensation. Developing nations are biodiversity- and knowledge-rich but face exploitation. The Basmati rice patent (1997, US company) and attempts to patent turmeric and neem are examples. India passed the second amendment of the Indian Patents Bill to address such issues.