Biotechnology stops being abstract the moment you see it in a hospital or a cotton field — insulin made by bacteria, pest-proof crops, gene therapy for a child with a missing enzyme. NEET regularly picks single-fact questions from this topic (names of genes, organisms, patients, proteins), so precise recall of examples matters as much as understanding the logic.
What "Applied Biotechnology" Means Here
Biotechnology in the modern sense means using living cells, or their molecular machinery, after deliberately editing their genetic instructions, to make a product or provide a service. The three broad arenas you must know are agriculture (genetically modified crops), medicine (recombinant therapeutics, gene therapy, molecular diagnosis) and industry/animal husbandry (transgenic animals, enzymes, biofuels).
An organism whose genome has been altered by inserting, deleting or modifying genes using recombinant DNA methods is called a genetically modified organism (GMO). If foreign DNA from another species has been stably introduced and is inherited, the organism is specifically called transgenic. Note the difference from conventional breeding: breeding shuffles genes already present within a species or close relatives, whereas transgenesis can move a gene across kingdoms — a bacterial gene into a plant, a human gene into a cow.
Why bother? Genetic modification can:
- Make crops tolerant to abiotic stresses (cold, drought, salt, heat).
- Reduce dependence on chemical pesticides by building pest resistance into the plant.
- Cut post-harvest losses and slow ripening.
- Increase mineral or vitamin content (biofortification) and improve nutritional quality.
- Increase efficiency of mineral uptake from soil.
- Produce cheap, safe, plentiful supplies of proteins that were earlier extracted from animal tissue.
Biotechnology in Agriculture: Bt Crops and RNA Interference
Bacillus thuringiensis is a soil bacterium that, during sporulation, deposits crystals of a protein toxic to certain insect larvae. The crucial point is that the crystal protein is produced as an inactive protoxin. When a caterpillar eats it, the insect's highly alkaline midgut dissolves the crystal and converts the protoxin into the active toxin. The activated toxin inserts into the midgut epithelial membrane, creates pores, the cells swell and lyse, and the larva dies. Because the bacterium's own gut chemistry (and ours, which is acidic) never activates the protoxin, the bacterium is unharmed and the protein is harmless to humans.
The genes encoding these proteins are named cry genes, and different cry genes target different insect groups:
- cryIAc and cryIIAb → protect against cotton bollworms.
- cryIAb → protects against corn borer.
Cotton carrying cryIAc/cryIIAb is the familiar Bt cotton; maize carrying cryIAb is Bt corn.
A second, cleverer strategy against pests is RNA interference (RNAi). RNAi is a natural cellular defence, present in all eukaryotes, in which a double-stranded RNA molecule triggers the silencing of a specific mRNA. The dsRNA is processed into small RNAs that bind complementarily to the target mRNA, blocking its translation or causing its destruction. The dsRNA source can be a transposon, a virus, or an engineered construct.
The classic NEET example is the nematode Meloidogyne incognita, a root-knot parasite of tobacco. Scientists introduced into the tobacco plant a construct that produces both the sense and antisense RNA of a nematode gene. Since the two transcripts are complementary, they pair up inside the plant cell to form dsRNA. When the nematode feeds, it takes up this dsRNA, its own essential mRNA is silenced, and the parasite cannot survive — the transgenic plant is protected without any chemical nematicide.
Other agricultural landmarks worth remembering: Flavr Savr tomato (delayed softening/ripening), Golden rice (β-carotene enriched), and Bt brinjal.
Biotechnology in Medicine: Insulin, Gene Therapy, Diagnosis
Recombinant therapeutics. Roughly 30 recombinant drugs are in worldwide clinical use, and India makes and markets a good number of them. The showpiece is human insulin.
Insulin in the pancreas is first made as pro-insulin, a single chain containing an extra stretch called the C-peptide. Mature insulin has two short polypeptides, chain A (21 amino acids) and chain B (30 amino acids), joined by disulphide bridges; the C-peptide is snipped out during maturation. Historically insulin was extracted from the pancreas of slaughtered cattle and pigs, which caused allergic reactions in some patients and was in limited supply. The engineering challenge was to assemble the mature, correctly folded two-chain hormone outside a pancreas.
In 1983, Eli Lilly solved it: the DNA sequences for chain A and chain B were separately introduced into E. coli, the two chains were produced separately, then extracted and combined by creating disulphide bonds — yielding humulin, human insulin identical to the natural hormone.
Gene therapy means correcting a hereditary defect by delivering a functional gene into the patient's cells or embryo. The first documented case, in 1990, involved a 4-year-old girl with adenosine deaminase (ADA) deficiency, a defect that cripples the immune system because the enzyme ADA is essential for lymphocyte function.
- Option 1: bone-marrow transplant — not always available or compatible.
- Option 2: enzyme replacement by injecting ADA — works, but is not a cure since it must be repeated.
- Option 3: gene therapy. Lymphocytes are removed from the patient's blood, a functional ADA cDNA is introduced using a retroviral vector, and the cells are returned to the body. Because mature lymphocytes are short-lived, the infusion must be repeated periodically. A permanent cure would require introducing the gene into bone-marrow stem cells at an early stage.
Molecular diagnosis. Conventional methods (serum tests, urine analysis) detect disease only after symptoms and pathogen load are substantial. Molecular techniques detect the pathogen or mutation much earlier:
- PCR amplifies tiny amounts of pathogen nucleic acid — used to detect HIV in suspected AIDS patients, to spot mutations in suspected cancer patients, and to identify many genetic disorders.
- ELISA works on antigen–antibody interaction: it detects either the pathogen's antigens or the antibodies the body has raised against them.
- Nucleic acid hybridisation with a radiolabelled probe on a clone or tissue sample reveals a mutated gene because a mutated sequence will not pair perfectly with the probe (detected by autoradiography).
Transgenic Animals
Animals whose genome has been altered by an added foreign gene are transgenic. Transgenic mice dominate the field numerically, but rats, rabbits, pigs, sheep, cows and fish have all been produced. They serve five broad purposes:
- Study of normal physiology and development — for instance, understanding how genes that regulate body growth or complex processes such as insulin-like growth factor action operate.
- Study of disease — animal models are made to carry human disease genes, so that treatments can be tested. Models exist for cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's disease.
- Biological products — a valuable human protein can be produced in an animal's milk. The example to remember is Rosie (1997), the first transgenic cow, whose milk contained the human protein alpha-lactalbumin at 2.4 g per litre, making it nutritionally more suitable for human babies than ordinary cow milk. (Human protein α-1-antitrypsin, used for emphysema, is another such product.)
- Vaccine safety testing — transgenic mice have been developed for testing the safety of the polio vaccine, replacing monkeys.
- Chemical safety testing (toxicity testing) — transgenic animals carrying genes that make them more sensitive to toxic substances reveal effects faster and at lower doses.
Ethics, Patents and Biopiracy
Because genetic manipulation can produce unpredictable results and raises moral questions about tampering with organisms, the Indian government set up the GEAC (Genetic Engineering Approval Committee) to judge the validity of GM research and the safety of introducing GM organisms for public use.
Patents and biopiracy. A patent grants exclusive commercial rights over an invention. Problems arise when firms in industrialised nations patent genetic resources or traditional knowledge taken from developing countries without authorisation or fair compensation — this is biopiracy.
Two cases regularly examined:
- Basmati rice: India has a huge diversity of scented rice; in 1997 a US company (RiceTec) obtained a patent on "basmati" lines derived from Indian varieties crossed with Western ones, claiming novel invention.
- Bt cotton and neem/turmeric-type cases illustrate similar disputes over ownership of biological material.
A famous engineered organism worth noting is the Pseudomonas putida strain created by Ananda Chakrabarty, which can degrade hydrocarbons in oil spills — the subject of a landmark patent decision on living organisms.
Indian law has been amended to protect indigenous knowledge and to ensure equitable sharing of benefits with the communities and farmers who conserved and developed these resources.
Common Mistakes and Exam Traps
- "Bt toxin kills the bacterium too." It does not. The protein exists as an inactive crystalline protoxin in Bacillus thuringiensis and needs the insect's alkaline gut to be activated. Do not write "acidic".
- Mixing up cry genes. cryIAc and cryIIAb → cotton bollworm; cryIAb → corn borer. Also remember the toxin gene is cry, not Bt gene as an official name.
- RNAi confusion. RNAi is triggered by double-stranded RNA, and in the tobacco–Meloidogyne incognita example the dsRNA forms in the plant (because both sense and antisense strands are transcribed there) but silences the nematode's mRNA. Also, RNAi is a natural defence mechanism, not an invention.
- Insulin details. Chain A = 21 amino acids, chain B = 30; the extra piece removed during maturation is the C-peptide, and Eli Lilly produced the chains separately in E. coli before joining them. A common wrong option says pro-insulin was made in E. coli and cleaved.
- Gene therapy is not permanent in the ADA case. Since mature lymphocytes are used, the treatment must be repeated; only stem-cell-level correction would be a full cure.
- Rosie's protein is human alpha-lactalbumin (2.4 g/L), not casein and not insulin.