Biotechnology and its Applications: Class 12 Biology · Chapter 10

Picture three scenes from one ordinary week in India. A cotton grower in Maharashtra sprays his field far less often than his father had to. A schoolgirl with type 1 diabetes injects insulin before her lunch. A laboratory reports a viral infection in a sample collected before the patient felt the slightest fever. Each scene quietly depends on biotechnology.

In its industrial sense, biotechnology (जैव प्रौद्योगिकी) means using living cells, or molecules taken from them, to make useful products on a large scale. Microbes, plants and animals, many of them engineered, now help to clean polluted soil and sewage, brew biofuels, make enzymes for food and detergents, and supply vaccines, medicines, test kits and better crops.

Moving a discovery from the bench to the market means solving three problems in turn (Fig. 10.1). First, find or build the best catalyst: a living one (generally a microbe improved by selection or engineering) or an isolated enzyme. Second, engineer the conditions in which that catalyst works fastest, which is the job of the bioreactor. Third, recover and purify the product until it is clean enough to sell, eat or inject; this is downstream processing.

This chapter follows those tools out of the laboratory: onto farms (Section 10.1), into hospitals and clinics (Section 10.2), into animals built for research and medicine (Section 10.3), and finally into the debates about who may change living things and who may own them (Section 10.4).

10.1 Biotechnological Applications in Agriculture

India must feed more than 1.4 billion people from roughly the same area of farmland it cultivated in the 1970s. Broadly, there are three ways to coax more food out of that land, and each has a price.

The Green Revolution of the 1960s and 1970s took the first route. High-yielding dwarf varieties of wheat and rice were combined with irrigation, fertilisers and pesticides, and India's foodgrain harvest has since grown about four-fold. The gains have slowed, however. Agrochemicals cost more than many small farmers can afford, they damage soil and water when overused, and conventional breeding is slow and can only add traits found in plants that can be crossed with the crop. Biotechnology opened further routes, beginning with growing whole plants from tiny pieces of tissue.

Tissue culture and micropropagation

Cut a disc from a leaf, sterilise it, lay it on a jelly of nutrients in a closed flask, and with the right hormones it can become a new plant with roots, shoots and flowers. The starting piece is an explant and the technique is tissue culture (ऊतक संवर्धन). Botanists worked this out in the 1950s; in 1958, for example, F. C. Steward raised whole carrot plants from small clusters of carrot-root cells. It works because of totipotency.

The culture medium is a complete diet set in a gel. A closed vessel lets in little carbon dioxide, so the explant cannot make enough food by photosynthesis and needs a carbon source, usually sucrose. Inorganic salts supply nitrogen, phosphorus, potassium and trace elements; vitamins and amino acids support metabolism; agar sets the mixture into a jelly. The deciding ingredients are the growth regulators, an auxin and a cytokinin. Their ratio steers development: a balance tends to give a callus (an unorganised lump of dividing cells), more cytokinin favours shoots and more auxin favours roots.

If the shoots that form are cut and moved to fresh medium again and again, a single explant can yield thousands of plantlets within months. This is micropropagation (सूक्ष्मप्रवर्धन). Since every plantlet arises from the parent by mitosis alone, all of them carry the same genes as that parent; such plants are called somaclones. A grower can therefore multiply one outstanding plant without the reshuffling of genes that seeds bring. (Occasionally the culture process itself causes small genetic changes, called somaclonal variation, so growers check their stocks.)

Banana is a striking example in India: tissue-culture plantlets of the Grand Naine variety are planted on a large scale because they are uniform, healthy and ready to harvest together. Tomato, apple, potato, sugarcane, orchids and many forest trees are also micropropagated commercially.

Virus-free plants from meristems

Viruses are a stubborn problem in crops grown from cuttings, tubers or suckers, because every new plant inherits its parent's infection. Yet even in a badly infected plant, the tiny dome of dividing cells at the shoot tip (the apical meristem) and the buds in the leaf axils (axillary meristems) are usually free of virus. Viruses move mainly through the plant's vascular tissue, which has not yet formed inside the meristem, and the meristem's cells divide faster than the virus can spread into them.

That gives growers an escape route (Fig. 10.3). Under a microscope, a technician removes a meristem a fraction of a millimetre long and grows it on culture medium; the plant that develops starts life clean. Potato seed-tuber programmes, sugarcane nurseries and banana producers all use meristem culture, followed by micropropagation to multiply the healthy plants.

Somatic hybridisation

Breeders normally combine two plants by cross-pollination, which only works between close relatives. Tissue culture offers a way around that barrier. Enzymes such as cellulase and pectinase digest the cell walls away, leaving naked protoplasts (जीवद्रव्यक) bounded only by their plasma membranes. Without walls in the way, protoplasts from two different plants can be made to fuse, using a chemical such as polyethylene glycol (PEG) or a brief electric pulse.

The fused cell carries the genetic material of both parents. In culture it rebuilds a wall, divides and can regenerate into a plant called a somatic hybrid; the process is somatic hybridisation (Fig. 10.4). The best-known attempt fused tomato and potato protoplasts to make the pomato. It grew, but it never combined a good crop of tomatoes with a good crop of potatoes, so it was of no commercial use. Somatic hybrids have been more successful at moving disease resistance from wild relatives into crops such as potato.

Genetically modified crops

Can our knowledge of genes help farmers harvest more while using fewer chemicals? Tissue culture copies or combines whole genomes; genetic engineering is more precise and moves just one or a few chosen genes. Plants, animals, bacteria or fungi whose genes have been altered this way are genetically modified organisms (GMOs, आनुवंशिकतः रूपांतरित जीव).

GM crops have been designed to solve problems that ordinary breeding struggled with:

• Built-in pest protection, so farmers spray less insecticide.
• Survival under abiotic stress: drought, cold, heat or salty soil.
• Better nutrition: golden rice makes β-carotene, which our bodies convert into vitamin A.
• Thriftier use of fertiliser: plants that take up nitrogen or phosphorus more efficiently drain the soil less.
• Longer shelf life: fruit engineered to soften slowly survives transport and storage, so less food is wasted.
• Plants as factories: crops engineered to yield industrial starches, biofuels, or vaccines and other drugs.

Two applications show how such crops are built: plants that make their own insecticide, and plants that silence a parasite's genes.

Bt cotton

Bacillus thuringiensis (Bt for short) is a soil bacterium. When it forms spores, it also packs proteins into microscopic crystals that are poisonous to certain insects. Farmers, organic farmers included, have sprayed Bt for decades as a biological pesticide. Genetic engineering went one step further: a toxin gene was isolated from the bacterium and inserted into crop plants, which now produce the insecticidal protein in their own leaves, stems and bolls. Bt cotton, Bt maize (corn) and Bt soybean are grown widely; Bt versions of rice, potato, tomato and brinjal have also been made, and farmers in Bangladesh grow Bt brinjal.

Each strain's toxin works on a narrow group of insects. In cotton the targets are caterpillars of moths, the lepidopterans (bollworms, budworms, armyworms). Other Bt strains are deadly to beetle larvae (coleopterans) or to the larvae of flies and mosquitoes (dipterans). Most other animals, people included, are not affected.

The answer is that the toxin is stored as an inactive protoxin. A caterpillar chewing a Bt leaf swallows the crystals. Its midgut is strongly alkaline (around pH 10 in many caterpillars), which dissolves them, and its own gut enzymes trim the protoxin into the active toxin. The active toxin binds to specific receptor proteins on the epithelial cells lining the midgut and inserts into their membranes, creating pores. Water and ions rush in, the cells swell and burst (lyse), the gut wall breaks down, and the insect stops feeding and dies within days (Fig. 10.5). Our stomach is acidic and our gut cells lack those receptors, so the protein is simply digested.

Bt toxins are called Cry proteins (from crystal), and the genes that encode them are cry genes. Hundreds are known, each active against a particular group of insects, so engineers pick the gene that matches the crop and its main pest (Table 10.1). Your textbook writes the names with roman numerals, as in cryIAc; current naming uses arabic numerals, cry1Ac. Both mean the same gene.

India approved its first Bt cotton hybrids, carrying cry1Ac, in 2002. A second generation with two genes, cry1Ac and cry2Ab, followed in 2006, so that a pest would have to resist two toxins at once. Today more than nine-tenths of India's cotton area is sown with Bt hybrids, and Bt cotton is still the only GM crop grown commercially in the country.

Bt crops have one weak point: evolution. The pink bollworm, which feeds hidden inside the cotton boll, has become resistant to both toxins across much of India, and farmers have had to go back to spraying against it. Resistance spreads fastest when every plant in a district carries the toxin, because then only resistant moths survive to mate. Growers are therefore asked to keep a refuge of non-Bt cotton, today often supplied as non-Bt seeds mixed into the seed packet, so that susceptible moths survive and mate with the rare resistant ones (Fig. 10.6).

Pest-resistant plants: RNA interference

Not every pest is an insect. Tiny roundworms called nematodes attack crops from below the soil. One of the most damaging is the root-knot nematode, Meloidogyne incognita. Its larvae enter the roots of tobacco and many other crops and turn root cells into feeding sites; the roots swell into knots (galls), water and minerals stop reaching the shoots, and much of the harvest is lost.

This time the weapon was borrowed from eukaryotic cells themselves. In RNA interference (RNAi), a double-stranded RNA (dsRNA) switches off any gene whose messenger RNA has the matching sequence. Where does such dsRNA come from in nature? Many viruses carry RNA as their genetic material and form dsRNA as they multiply, and some transposons (‘jumping genes’) copy themselves by way of RNA. Healthy cells rarely contain long dsRNA, so it works as a danger signal, and RNAi lets the cell destroy the matching messages.

Inside a cell, an enzyme called Dicer chops the dsRNA into short pieces about 21–23 nucleotides long, the small interfering RNAs (siRNAs). A protein complex called RISC keeps one strand of each piece as a guide, finds any mRNA with the complementary sequence, and cuts it or blocks its translation. The gene is still present, but its message never becomes protein.

The plan was to make the tobacco plant itself produce the trigger. Researchers chose genes that the nematode cannot live without and, with Agrobacterium as the vector, gave tobacco a copy of the nematode sequence arranged so that the plant transcribed it in both directions, giving sense RNA and the complementary antisense RNA. The two strands paired into dsRNA inside the plant's cells (Fig. 10.7). When a nematode fed on the roots it took in this dsRNA, its own RNAi machinery silenced the matching mRNA, and the parasite could not survive. Roots of these transgenic plants stayed largely free of the galls that covered the roots of ordinary plants.

10.2 Biotechnological Applications in Medicine

Before recombinant DNA technology, many protein medicines had to be extracted from animal organs or donated human blood. Supplies were limited, batches varied, a foreign protein could provoke the immune system, and donor material could carry hidden infections. Engineered cells changed this. They make human proteins, identical to our own, in fermenters of any size, and because the body recognises these proteins as its own, allergic and immune reactions become rare and no donor infection can slip through.

Your textbook mentions about 30 recombinant therapeutics approved worldwide; the count today runs to several hundred. India makes many of them, including low-cost biosimilars, and in 1997 a Hyderabad company launched India's first home-grown recombinant vaccine, against hepatitis B. Some examples are listed in Table 10.2.

10.2.1 Genetically Engineered Insulin

Insulin, a hormone from the beta cells of the pancreas, lets body cells take up glucose from the blood. People with type 1 diabetes make almost none and need insulin every day; many people with long-standing type 2 diabetes need it too. An ICMR study published in 2023 estimated that about 101 million Indians have diabetes, so the demand is enormous.

For about sixty years after its discovery in 1921, people with diabetes relied on insulin purified from the pancreas glands of pigs and cattle collected at abattoirs. The animal hormone works because it is almost the same molecule: pig insulin differs from ours at one amino acid out of 51, and cattle insulin at three. But a minority of patients reacted to it as a foreign protein, with allergies or antibodies, and supplies depended on the meat trade. A bacterium that made human insulin would solve both problems: to get more insulin, simply grow more bacteria.

Mature insulin is a small protein: chain A of 21 amino acids and chain B of 30, held together by two disulphide bridges (–S–S–), with a third bridge inside chain A. The pancreas does not make the two chains separately, though. It makes one chain, proinsulin, a pro-hormone that becomes active only after processing (compare pepsinogen, which turns into active pepsin only when part of it is cut away). In proinsulin a connecting stretch, the C peptide, joins the end of chain B to the start of chain A. The chain folds, the bridges form, and enzymes then cut out the C peptide, releasing mature insulin (Fig. 10.8).

Bacteria cannot carry out this processing, and that was the main obstacle to making insulin by recombinant DNA technology. The way round it, used by the American company Eli Lilly with methods developed at Genentech, was to make the two chains in separate bacterial cultures and assemble them afterwards. A short synthetic gene was made for each chain, and each gene went into its own E. coli plasmid, so one batch of bacteria turned out A chains and the other B chains. After purification the chains were brought together under conditions in which the right disulphide bridges form, and the result was human insulin (Fig. 10.9). Approved in the USA in 1982 and on sale from 1983, it was the first medicine made by recombinant DNA technology.

The product has exactly the amino acid sequence of the natural hormone. Later processes make proinsulin itself in microbes and cut out the C peptide with enzymes in the factory. Many manufacturers, several of them in India, now make insulin in E. coli or in yeast, along with insulin analogues in which one or two amino acids are deliberately changed so that the insulin acts faster or lasts longer.

10.2.2 Gene Therapy

Most medicines for inherited diseases treat the effects of a faulty gene, for example by injecting the protein the patient cannot make. Gene therapy (जीन चिकित्सा) goes after the cause: instead of supplying the missing product again and again, it supplies the instructions for making it. A working copy of the gene is delivered into the patient's cells, where it does the job that the faulty copy cannot.

The usual delivery vehicles are disabled viruses. Viruses naturally carry their genes into the cells they infect; in a vector, the disease-causing genes are removed and the therapeutic gene takes their place.

The first approved clinical gene therapy took place in the USA in 1990. The patient, then four years old, had adenosine deaminase (ADA) deficiency. ADA is an enzyme that clears deoxyadenosine, a by-product of DNA breakdown. Without it the by-product builds up and kills developing lymphocytes, so the immune system barely works and the child falls ill with one infection after another; the condition is a form of severe combined immunodeficiency (SCID). It is caused by a faulty or missing ADA gene inherited from both parents.

Children with ADA deficiency can be kept alive with regular injections of the working enzyme (enzyme replacement therapy), but these help only partly and must continue for life. A bone marrow transplant can cure the disease, yet only if a well-matched donor is found, and many children have none.

The 1990 team worked outside the body (Fig. 10.10). Lymphocytes were separated from the girl's blood and multiplied in culture; a disabled retrovirus was used to insert a working ADA gene, as cDNA, into them; and the engineered cells were dripped back into her bloodstream, where they made ADA. Mature lymphocytes cannot go on dividing for ever, though, so their numbers fell and fresh infusions were needed every few months.

A lasting cure needs the gene in cells that go on producing new lymphocytes. Your textbook notes that introducing the gene into cells at an early embryonic stage could be permanent. Changing an embryo, however, also changes the eggs or sperm it will later make, so the change would pass to future generations. Such germline gene therapy is not permitted under India's national guidelines for gene therapy (ICMR, 2019) and is banned or tightly restricted in most countries. The route actually used is the patient's own blood-forming stem cells from the bone marrow: corrected once, they keep making healthy lymphocytes. A treatment of this kind for ADA deficiency was approved in Europe in 2016.

10.2.3 Molecular Diagnosis

Imagine a virus that takes two weeks to cause fever. During those two weeks the patient feels well, may infect others, and could already have benefited from treatment. Tests that look for the effects of a disease (changes in serum or urine) or that need many microbes (a microscope slide, a culture) usually turn positive only after the pathogen has multiplied and symptoms appear. Molecular methods look directly for the pathogen's own molecules, its DNA, RNA or proteins, and can find them while they are still scarce. Three tools are central: recombinant DNA probes, the polymerase chain reaction (PCR) and ELISA (Table 10.3).

PCR solves the problem by copying. Each cycle can at most double the target sequence (an RNA virus is first copied into DNA by reverse transcriptase). Ten cycles multiply it about a thousand times ($2^{10}$ is 1024), and thirty cycles about a billion times. So even a handful of copies grows into an amount a detector can see, long before symptoms appear (Fig. 10.11).

PCR is used to confirm HIV infection in infants and to track the amount of virus in patients, to detect tuberculosis and its drug resistance, and, during the COVID-19 pandemic, it was the standard test for SARS-CoV-2. India's own chip-based PCR test for tuberculosis, Truenat, was endorsed by the World Health Organization in 2020. PCR also finds mutations in cancer cells and in genes behind inherited disorders such as sickle-cell anaemia and thalassaemia.

A probe is a short single strand of DNA or RNA that carries a label, traditionally a radioactive atom and today often a fluorescent dye. It sticks (hybridises) only to DNA whose bases are complementary to its own. To test a set of cloned cells, their DNA is fixed onto a membrane, the probe is washed over it and any unbound probe is rinsed off. Wherever the probe has paired, a spot appears on X-ray film (autoradiography) or under a scanner. A clone whose gene is mutated in the probed region cannot pair with the probe and gives no spot (Fig. 10.12).

ELISA (enzyme-linked immunosorbent assay) works with proteins rather than nucleic acids. Its key ingredient is an antibody that recognises one target and nothing else. Depending on the disease, the test is designed to catch either the microbe's own molecules, its antigens (proteins or glycoproteins), which show it is present now, or the antibodies the patient has made against it, which show that the immune system has met it.

In a common form, the 'sandwich' ELISA, a plastic well is coated with antibodies that capture the antigen. A second antibody, linked to an enzyme, then binds to any captured antigen. When a colourless substrate is added, the enzyme converts it into a coloured product; the deeper the colour, the more antigen there was (Fig. 10.13). ELISA is used to screen donated blood for HIV and hepatitis B and to detect the dengue virus's NS1 antigen in the first days of fever.

10.3 Transgenic Animals

A mouse that glows green under blue light because it carries a jellyfish gene is a transgenic animal (पारजीनी जंतु): a gene from another source has been built into its DNA and is working there. Mice make up more than 95 per cent of all transgenic animals, because they are small, cheap to keep, breed every few weeks and have very well understood genes. Fish, pigs, cows, sheep, goats, rabbits and rats have been made transgenic too.

A common method injects copies of the chosen gene, joined to a promoter that switches it on in the right tissue, into a fertilised egg. The embryos are placed in a foster mother, and the young are tested to find those that have taken up the gene (Fig. 10.14). Genome-editing tools such as CRISPR–Cas9 now make such changes more precisely.

Why go to this trouble? Five reasons stand out (Table 10.4).

The biological-products route is sometimes nicknamed 'pharming'. Proteins too complex for bacteria to make correctly can be collected from an animal's milk without harming it, and similar work has aimed at treatments for phenylketonuria (PKU) and cystic fibrosis. Disease models matter just as much: a mouse that develops a human illness lets researchers test a treatment before any person is exposed to it.

10.4 Ethical Issues

The power to rewrite genes raises questions that science alone cannot settle. Is it right to give an animal a disease for research? Should a gene from a bacterium end up in our food? Who gains, and who carries the risk? Such questions are settled not in the laboratory but through ethics and law: agreed standards for what may be done to living things, and official bodies that enforce them.

There are biological reasons for caution too. A GM organism released into fields becomes part of an ecosystem, with effects that are hard to predict: its genes might pass to wild relatives through pollen, a toxin might harm insects other than the target, pests might evolve resistance (as the pink bollworm has), and a new protein in food must be checked for allergy. Each release is therefore judged case by case.

In India, GM research and release are governed by rules framed in 1989 under the Environment (Protection) Act, 1986. Work begins in a laboratory overseen by its Institutional Biosafety Committee (IBSC). The Review Committee on Genetic Manipulation (RCGM), under the Department of Biotechnology, reviews research and small, confined field trials. The Genetic Engineering Appraisal Committee (GEAC), under the Ministry of Environment, Forest and Climate Change, appraises large field trials and the release of GM organisms and products into the environment, and the government takes the final decision (Fig. 10.15). Your textbook uses the committee's older name, Genetic Engineering Approval Committee; it was renamed in 2010.

The same system has produced very different outcomes. Bt cotton was approved in 2002. Bt brinjal was cleared by GEAC in 2009, but in 2010 the government placed a moratorium on its release, which has not been lifted. GEAC's 2022 approval for the environmental release of GM mustard was challenged in the Supreme Court. Since 2022, plants that have been genome-edited without inserting any foreign DNA have been exempt from the GMO rules, and in 2025 India released its first two genome-edited rice varieties.

Patents and biopiracy

A second set of questions is about ownership. A patent is a right granted by a government for a limited period, 20 years in India, that lets the inventor stop others from making, using or selling an invention without permission. To be patentable, an invention must be new, involve an inventive step and be useful. Engineered microbes, genes and processes can be patented in many countries. The trouble starts when someone patents a plant, a remedy or a crop variety that farmers or tribal communities discovered and improved long ago, as if it were new.

Basmati shows how such a dispute unfolds. This aromatic long-grain rice is the work of generations of farmers on the Indo-Gangetic plains of India and Pakistan, a region with some of the richest rice diversity on Earth. In 1997 a Texas company, RiceTec, obtained a US patent for rice lines it had bred from Basmati crossed with semi-dwarf rice. Some of its claims were worded broadly enough to reach rice resembling Basmati itself, which alarmed Indian farmers and exporters. India challenged the patent in 2000, and by 2001 most claims had been withdrawn or rejected, leaving only three specific rice lines protected. India has since registered Basmati as a geographical indication (GI) for rice from a defined region.

Other patents targeted traditional Indian remedies. A US patent granted in 1995 on using turmeric to heal wounds was revoked in 1997, after India's Council of Scientific and Industrial Research (CSIR) showed from old Sanskrit texts and a 1953 journal article that the use was long known. A European patent on an antifungal extract of neem oil, granted in 1994, was revoked in 2000. To make such challenges easier, India built the Traditional Knowledge Digital Library (TKDL), which turns ancient texts on Ayurveda, Unani, Siddha and yoga into records that patent examiners anywhere can search.

Why does this matter so much? Look at a map of the world's biodiversity: tropical countries such as India, Brazil and Indonesia hold most species, while most biotechnology companies and research money are in North America, Europe and Japan. A healer's knowledge that a certain leaf stops bleeding is a ready-made lead, and a company that follows it skips years of blind screening. Fairness demands that the community whose knowledge started the search shares in what it earns (compare the two paths).

Nations have responded with laws. India amended its Patents Act in 2002 (the second amendment your textbook refers to) and again in 2005: traditional knowledge cannot be patented as an invention, and applicants must disclose the source and geographical origin of any biological material they used. The Biological Diversity Act, 2002 (amended in 2023) requires foreign users of Indian bio-resources, and anyone seeking a patent based on them, to obtain the approval of the National Biodiversity Authority, and requires benefits to be shared with the communities that conserve them. Internationally, the Convention on Biological Diversity (1992) and its Nagoya Protocol (2010) set out the same principle of access with benefit sharing.