Biotechnology and its Applications – Class 12 Biology Chapter 10 Notes & NCERT PDF

Introduction

Chapter 9 taught you the tools of biotechnology (restriction enzymes, vectors, PCR). Chapter 10 shows what those tools actually produce. The NCERT text organises the applications into three big areas — agriculture, medicine and transgenic animals — and ends with the ethical issues of patents and biopiracy. Board papers love this chapter because every topic is a neat "name the organism / name the gene / explain the mechanism" question. Read it as a set of case studies: Bt cotton, RNAi tobacco, recombinant insulin, ADA gene therapy, Rosie the cow and Basmati rice.

Key Concepts

10.1 Biotechnological Applications in Agriculture

The book lists three options for increasing food production: agro-chemical based agriculture, organic agriculture and genetically engineered crop-based agriculture. The Green Revolution tripled food supply but not enough for a growing population, and it depended on fertilisers and pesticides that are costly and harmful.

Genetically Modified Organisms (GMOs) are plants, bacteria, fungi and animals whose genes have been altered by manipulation. GM plants have: (i) more tolerance to abiotic stresses (cold, drought, salt, heat); (ii) reduced reliance on chemical pesticides (pest-resistant crops); (iii) reduced post-harvest losses; (iv) increased efficiency of mineral usage (prevents early exhaustion of soil fertility); (v) enhanced nutritional value — Golden rice, rich in Vitamin 'A'. GM plants are also used to create tailor-made plants that supply alternative resources (starches, fuels, pharmaceuticals) to industry.

Bt cotton. Bt toxin comes from the soil bacterium Bacillus thuringiensis. Some strains produce proteins that kill lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). The bacterium forms crystals of the protein during a particular growth phase; the toxin does not kill the bacterium because it exists as an inactive protoxin. Once an insect ingests it, the alkaline pH of the gut solubilises the crystals and converts it into the active toxin. The active toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis, and the insect dies. The toxin is coded by genes called cry. Proteins encoded by cryIAc and cryIIAb control cotton bollworms; cryIAb controls corn borer.

Pest-resistant plants — RNAi. The nematode Meloidegyne incognitia infects the roots of tobacco and reduces yield. RNA interference (RNAi) is a method of cellular defence in all eukaryotes: a specific mRNA is silenced by a complementary double-stranded RNA (dsRNA) that binds to and prevents its translation. Using Agrobacterium vectors, nematode-specific genes were introduced into the host plant so that both sense and anti-sense RNA were produced. These two complementary RNAs formed dsRNA, which silenced the parasite's mRNA. The parasite could not survive in the transgenic host, which was thus protected.

10.2 Biotechnological Applications in Medicine

Recombinant DNA technology allows mass production of safe and more effective therapeutic drugs that do not cause unwanted immunological responses (a problem with products from non-human sources). About 30 recombinant therapeutics have been approved worldwide; 12 are marketed in India.

10.2.1 Genetically engineered insulin. Insulin from slaughtered cattle and pigs caused allergy in some patients. Human insulin is made of two short polypeptide chains, A and B, linked by disulphide bridges. In humans it is synthesised as a pro-hormone (pro-insulin) with an extra stretch, the C peptide, which is removed during maturation. The main challenge was assembling mature insulin. In 1983, Eli Lilly (an American company) prepared two DNA sequences corresponding to chains A and B, introduced them into plasmids of E. coli, produced the chains separately, extracted them and combined them by creating disulphide bonds to form human insulin.

10.2.2 Gene therapy corrects a gene defect diagnosed in a child or embryo by delivering a normal gene into the person's cells. The first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency. ADA is crucial for the immune system. Treatments include bone marrow transplantation or enzyme replacement therapy (injection of functional ADA), but neither is fully curative. In gene therapy, lymphocytes from the patient's blood are grown in culture, a functional ADA cDNA is introduced using a retroviral vector, and the cells are returned to the patient. Since these cells are not immortal, the patient needs periodic infusion. If the ADA gene from marrow cells is introduced into cells at early embryonic stages, it could be a permanent cure.

10.2.3 Molecular diagnosis. Conventional methods (serum and urine analysis) cannot detect a disease early. PCR amplifies nucleic acid, so very low concentrations of a pathogen can be detected; it is used to detect HIV in suspected AIDS patients and mutations in genes of suspected cancer patients. A single-stranded DNA or RNA tagged with a radioactive molecule (probe) hybridises with its complementary DNA in a clone of cells and is detected by autoradiography; a clone with a mutated gene will not appear on the film because the probe does not complement it. ELISA is based on the principle of antigen–antibody interaction; infection can be detected by the presence of antigens (proteins, glycoproteins) or antibodies synthesised against the pathogen.

10.3 Transgenic Animals

Animals whose DNA has been manipulated to possess and express an extra (foreign) gene. Transgenic rats, rabbits, pigs, sheep, cows and fish exist, but over 95 per cent are mice. Reasons: (i) normal physiology and development — e.g. study of insulin-like growth factor; (ii) study of disease — models for cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's; (iii) biological products — human protein α-1-antitrypsin for treating emphysema, attempts for phenylketonuria (PKU) and cystic fibrosis; in 1997 the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre) containing human alpha-lactalbumin, nutritionally more balanced for human babies than natural cow milk; (iv) vaccine safety — transgenic mice used to test the safety of the polio vaccine; (v) chemical safety testing (toxicity testing).

10.4 Ethical Issues

The Indian Government has set up the GEAC (Genetic Engineering Approval Committee), which decides on the validity of GM research and the safety of introducing GM organisms for public services. Biopatents: in 1997 an American company got patent rights on Basmati rice through the US Patent and Trademark Office, which allowed it to sell a "new" variety derived by crossing an Indian variety with semi-dwarf varieties. India has an estimated 200,000 varieties of rice; 27 documented varieties of Basmati are grown in India. Other attempts: turmeric, neem. Biopiracy is the use of bio-resources by multinational companies without proper authorisation from the countries and people concerned and without compensatory payment. The Indian Parliament cleared the second amendment of the Indian Patents Bill to address such issues.

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