Biotechnology has moved rapidly from the laboratory to practical applications that touch almost every aspect of modern life. The previous chapter described the tools and processes of recombinant DNA technology; this chapter surveys the remarkable applications of these techniques in agriculture, medicine and the environment. Genetically modified organisms, produced by inserting foreign genes into their genomes, have transformed agriculture and medicine, and their applications continue to expand.
The chapter covers genetically modified organisms (GMOs) and their applications in agriculture, the production of therapeutic products like human insulin, gene therapy for genetic diseases, molecular diagnosis, and transgenic animals. It also addresses the ethical, social and regulatory issues associated with the application of biotechnology, including biopiracy and intellectual property rights. A balanced understanding of both the benefits and the risks of biotechnology is essential for a responsible citizen and future scientist.
Agriculture has been a major beneficiary of biotechnology. The two main approaches are the production of pest resistant plants and the improvement of crop quality, primarily through the development of genetically modified (GM) crops.
Genetically modified organisms (GM or transgenic organisms) are plants, animals or microbes in which the genetic material has been altered by the insertion of a foreign gene. The advantages of GM crops are: - Tolerance to abiotic stresses like cold, drought, salt and heat. - Reduced reliance on chemical pesticides (pest resistant crops). - Reduced post-harvest losses. - Increased efficiency of mineral usage by plants. - Enhanced nutritional value of food, e.g., golden rice enriched with vitamin A.
Bt cotton is the most widely grown GM crop. It is produced by inserting the toxin gene (cry gene) from the bacterium Bacillus thuringiensis into the cotton genome. The Bt toxin is a protein that kills the cotton bollworm and other insect pests.
The mechanism of Bt toxin action: - The Bt toxin is initially produced as an inactive protoxin. - When an insect feeds on the plant, the alkaline pH of the insect gut activates the protoxin into the active toxin. - The activated toxin binds to the cells of the insect's gut, creating pores, which leads to the death of the insect.
Different cry genes code for toxins specific to different insects. For example, the cryIAc and cryIIAb genes control cotton bollworms, and the cryIAb gene controls corn borers.
RNA interference (RNAi) is a method of developing pest resistant plants by silencing a specific mRNA. It is used to develop plants resistant to nematode pests. In this method, a gene coding for a double stranded RNA that is complementary to the mRNA of the nematode is introduced into the host plant. When the nematode feeds on the plant, the double stranded RNA enters its body and silences the specific mRNA of the pest, preventing its translation and thus preventing the pest from reproducing. RNAi was used to develop tobacco plants resistant to the Meloidogyne incognita nematode.
Diabetes mellitus is a disease in which the body either does not produce enough insulin or cannot use the insulin it produces. The treatment requires the administration of insulin. Traditionally, insulin was extracted from the pancreas of slaughtered pigs and cattle, but animal insulin differs from human insulin by a few amino acids, which can cause allergic reactions in some patients.
The challenge of producing human insulin using recombinant DNA technology was solved by Eli Lilly in 1983. The approach was: - The genes for the two polypeptide chains of insulin (chain A and chain B) were synthesised separately and inserted into the plasmid of E. coli. - The E. coli cells produced the A and B chains separately. - The A and B chains were then combined by disulphide bonds to form functional human insulin.
An alternative approach was to produce a proinsulin (with the C peptide) and then remove the C peptide to obtain functional insulin. The recombinant insulin is identical to human insulin and does not cause the allergic reactions associated with animal insulin. This was the first-ever pharmaceutical product produced by genetic engineering.
Gene therapy is the treatment of genetic diseases by inserting a functional gene into the cells of the patient to correct the defective gene. It involves the delivery of the normal gene into a patient's cells, usually using a viral vector.
Gene therapy was first used in 1990 for the treatment of SCID (Severe Combined Immuno Deficiency), which is caused by the deficiency of the enzyme adenosine deaminase (ADA). The approach was: - Lymphocytes from the patient's blood were collected. - The functional ADA gene was introduced into the lymphocytes using a retrovirus as a vector. - The genetically engineered lymphocytes were then reintroduced into the patient's blood. - Since these lymphocytes are not immortal, the patient required periodic infusions of the engineered lymphocytes. As an alternative, bone marrow cells producing ADA were engineered and transplanted into the patient.
Gene therapy can be performed on somatic cells (somatic gene therapy, not inherited) or germ cells (germ line gene therapy, inherited by offspring).
Accurate diagnosis is essential for treatment. Techniques used for early and accurate diagnosis include: - PCR (Polymerase Chain Reaction): Used to detect the presence of very low amounts of pathogens or abnormal genes by amplifying their DNA. - ELISA (Enzyme Linked Immuno Sorbent Assay): Used to detect antibodies or antigens, e.g., for the diagnosis of AIDS. - Recombinant DNA technologies and DNA probes to detect mutations in genes.
Transgenic animals are animals whose genomes have been altered by the insertion of foreign genes. The common examples are mice, and their uses include: - Study of diseases: Transgenic models are developed to study the role of genes in disease development and to test treatments. - Biological products: Transgenic animals that carry genes for human proteins can produce these proteins in their milk, e.g., transgenic cows that produce human protein alpha-1-antitrypsin and transgenic goats producing a human protein for treating emphysema. - Vaccine safety: Transgenic mice are used to test the safety of vaccines before they are given to humans. - Chemical safety testing: Transgenic animals are used to test the toxicity of chemicals.
The use of biotechnology raises several ethical and social issues. The debate revolves around the safety of genetically modified food, the impact on biodiversity, and the fair sharing of benefits.
Biopiracy is the use of bioresources by multinational companies and other organisations without proper authorisation and without compensating the countries or communities from which they are obtained. For example, some organisations have tried to patent biological resources from developing countries, such as certain plants with medicinal properties. Most developed countries are now realising the unfairness of this practice. In response, an international agreement has been reached at the Convention on Biological Diversity (CBD) in 1992, which requires that countries and communities be consulted and compensated for the use of their bioresources and traditional knowledge.
Patents are exclusive rights granted to an inventor over their invention for a specific period. In the context of biotechnology, patents cover GM organisms, genes, and the processes of producing them. India has faced disputes over patents on biological resources like basmati rice and neem. It is important to balance the incentive to innovate (through patents) with the fair sharing of benefits with the original custodians of the biological resources.
| Application | Technology | Example |
|---|---|---|
| Pest resistance | Bt gene insertion | Bt cotton |
| Pest resistance | RNA interference | Nematode resistant tobacco |
| Nutrition | Golden rice | Vitamin A enriched rice |
| Medicine | Recombinant insulin | Human insulin from E. coli |
| Medicine | Gene therapy | SCID treatment |
| Diagnosis | PCR, ELISA | AIDS, genetic diseases |
| Step | Event |
|---|---|
| 1 | Bt protoxin ingested by insect |
| 2 | Activated by alkaline pH of insect gut |
| 3 | Toxin binds to gut cell membranes |
| 4 | Pores form, insect dies |
| Use | Example |
|---|---|
| Study of diseases | Transgenic mouse models |
| Biological products in milk | Transgenic cow, goat |
| Vaccine safety testing | Transgenic mice |
| Chemical safety testing | Transgenic animals |
Biotechnology and its applications demonstrate the power of genetic engineering to address real-world problems in agriculture, medicine and beyond. Genetically modified crops like Bt cotton and nematode resistant tobacco reduce dependence on chemical pesticides, while golden rice promises improved nutrition. In medicine, recombinant human insulin has replaced animal insulin for diabetic patients, gene therapy offers hope for genetic disorders like SCID, and molecular diagnostic tools like PCR and ELISA enable early detection of diseases. Transgenic animals serve as valuable models for studying disease and producing therapeutic proteins. At the same time, the chapter reminds us of the ethical responsibilities that accompany this power, from avoiding biopiracy to respecting intellectual property and sharing benefits fairly. A responsible application of biotechnology can thus improve human welfare while safeguarding biodiversity and justice.