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Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 Chapter Contents Biotechnological Applications in Agriculture Biotechnological Applications in Medicine Transgenic Animals Ethical issues Biotechnology can be defined as the use of biological processes in industry and technology, one of the reasons why biotechnology has received so much attention during the past three decades is because of gene cloning. Although many useful products can be obtained from microbial culture, the list in the past has been limited to those compounds naturally synthesized by micro organisms. Many important pharmaceuticals, which are produced not by microbes, but by higher organisms, could not be obtained in this way. This has been changed by the application of gene cloning to biotechnology. The ability to clone genes means that a gene for an important animal or plant protein can now be taken from its normal host, inserted into a cloning vector, and introduced into a bacterium as shown in figure. Chromosomes Gene encoding animal protein Vector carrying animal gene Animal Cell Animal protein mRNA Genetically engineered bacterium synthesizing the animal protein Fig. : A possible scheme for the production of an animal protein by a bacterium. mRNA = messenger RNA. If manipulations are performed correctly the gene will be expressed and the recombinant protein synthesized by the bacterial cell. It may then be possible to obtain large amount of the protein through batch cultures or continuous cultures. Chapter 19 Biotechnology and its Applications
Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 108 Biotechnology and its Applications NEET BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE In the last century, an all round development in various fields significantly improved the quality of life of the people that consequently had an explosive impact on the growth of population. Such increase in growth rate would lead to an absolute scarcity of basic requirements such as food. Many people had sensed this imminent disaster and were trying to work towards finding a solution. Three options were considered for increasing food production: (i) Agro-chemical based agriculture This involves the use of agrochemicals that is chemical products used in agriculture. It includes broad range of pesticides, including insecticides, herbicides and fungicides. They also include synthetic fertilizers, hormones and other chemical growth agents and concentrated stores of raw animal manure. (ii) Organic agriculture/farming In this, farmers use manure, biofertilizers, biopesticides and biocontrols to increase the crop production instead of using artificial fertilizers and pesticides. Organic farming works in harmony with nature rather than against it. This involves using techniques to achieve good crop yields without harming the natural environment or people who live and work in it. (iii) Genetically engineered crop-based agriculture Among the pioneers, was Norman E. Borlaug recognised as father of Green Revolution. What is Green Revolution? Period in which significant increase in agricultural productivity of grains (particularly wheat and rice) was observed in 20th century, resulting from (i) Introduction of improved crop varieties i.e., high-yielding varieties. (ii) Better management practices (irrigation, mechanisation and soil conservation technique). (iii) Use of agrochemicals (fertilisers or pesticides). Its early dramatic success was in Mexico and the Indian subcontinent. The green revolution succeeded in tripling the food supply, yet it was not enough to feed the growing human population. Hinderances: Green Revolution was not a complete success in developing world due to various factors:  For farmers in developing world, agrochemicals are often too expensive.  Further increases in yield with existing varieties is not possible using conventional breeding.  The new varieties required large amounts of fertilizers, and pesticides to produce high yields, raising concern about cost and potentially harmful effects.  Minimising the use of fertilizers and chemicals so that their harmful effects on the environment are reduced. Use of genetically modified crops is a possible solution to overcome the above stated problems Gene cloning provides a new dimension to crop breeding by enabling directed changes to be made to the genotype of a plant, circumventing the random processes inherent in conventional breeding. Two general strategies have been used : (a) Gene addition : Cloning is used to alter the characteristics of a plant by providing it with one or more new genes.
Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 NEET Biotechnology and its Applications 109 (b) Gene Subtraction : Genetic engineering techniques are used to inactivate one or more of the plant’s existing genes. Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called genetically modified organism (GMO) or transgenic organisms. Transgenic plants are useful in many ways. Genetic modification is useful because it has : (i) Made crops more tolerant to abiotic stresses (cold, drought, salt, heat). (ii) Reduced reliance on chemical pesticides (pest-resistant crops). (iii) Helped to reduce post harvest losses. (iv) Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil). (v) Enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice. The Science behind Golden Rice : Golden rice was developed by Ingo Potrykus and Peter Beyer to combat vitamin A and Iron deficiency as this could accumulate more -carotene. Golden rice is a transgenic variety of rice (Oryza sativa) which contains good quantities of -carotene (provitamin A - inactive state of vitamin A). -carotene is a principal source of vitamin A. Since the grains (seeds) of rice are yellow in colour due to -carotene, the rice is commonly called golden rice. It is a transgenic variety of rice with genes for synthesis of -carotene taken from the temperate garden favourite Daffodil (Narcissus pseudonarcissus) and inserted into the genome of a temperate strain of rice using Agrobacterium tumefaciens, as the vector to effect the transfer. The grains of this GM rice are similar to other varieties, in their crinkly and scabrous husk but the core of the grain is pale yellow instead of pearly white due to -carotene, which makes this the Golden rice, more so because -carotene is very important to our health. GM plants have been used to create tailor-made plants to supply the following: (i) Pharmaceuticals : Production of Hirudin by Brassica napus. (ii) Alternative resources to industries in the form of fuel : Oil seed is at present used mainly for margarine and other food oils, but it can be modified to produce fatty acids for detergent, substitute fuels and petrochemicals. Production of hirudin from transgenic Brassica napus seeds. Fig. : Transgenic Brassica napus Introduced into Brassica napus Seeds containing hirudin Isolation and purification Synthetic hirudin gene Purified Down-stream hirudin processing Hirudin is a naturally occurring, anticoagulant produced and secreted in the salivary glands of the medicinal leech, Hirudo medicinalis, with a number of desirable properties. Hirudin has been made in variety of microorganisms including yeast and E. coli but these entail significant costs associated with fermentation. Therefore, the gene-encoding hirudin was chemically synthesized and introduced into Brassica napus using Agrobacterium-mediated transformation. The resulting transgenic plant yielded seeds in which hirudin accumulates. The hirudin is purified and used as medicine. In this case, the transgenic product itself is the product of interest.
Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 110 Biotechnology and its Applications NEET Plants that make their own insecticides Plants are subject to predation by virtually all other types of organism - viruses, bacteria, fungi and animals but in agricultural settings the greatest problems are caused by insects. To reduce losses, crops are regularly sprayed with insecticides. Application of biotechnology led to development of pest resistant plants which could decrease the amount of pesticide used as discussed below : The endotoxins of Bacillus thuringiensis Insects not only eat plants; bacteria also form occasional part of their diet. In response, several types of bacteria have evolved defense mechanisms against insect predation, an example being B. thuringiensis which, during sporulation, forms intracellular crystalline bodies that contain an insecticidal protein called the endotoxin. The endotoxin that accumulates in the bacterium is an inactive precursor. After ingestion by the insect, this protoxin is cleaved by proteases (alkaline conditions in gut), resulting in shorter versions of the protein that display the toxic activity, by binding to the inside of the insects mid gut and damaging the surface epithelium by creating pores that cause swelling and lysis. So, that insect is unable to feed and consequently starves to death. This toxin called Bt toxin as produced by Bacillus thuringiensis has been cloned in bacteria and been expressed in plants to provide resistance to insects without the need for insecticides in effect created a bio-pesticide. Examples are Bt cotton, corn, rice, tomato, potato and soyabean etc. Specific Bt. toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton. The choice of gene depends on the crop and the pest as most Bt toxins are insect group specific. This toxin is encoded by a gene cry IAc named cry. These genes are effective against various types of insects e.g., Lepidopterans (tobacco budworm, armyworm), Coleopterans (beetles) and dipterans (flies and mosquitoes). There are a number of such genes for instance, the proteins encoded by gene cry IAc and cry llAb controls cotton bollworm, while that of cry IAb controls cornborer. (a) (b) Fig. : Cotton boll: (a) destroyed by bollworms; (b) a fully mature cotton boll Damages the gut epithelial cells Active toxin Proteinase digestion- in the insect gut Inactive protein -endotoxin gene Expression in the bacterium Fig. : Mode of action of a -endotoxin The gene transfer technology for corn is a recent achievement. The development of corn plants expressing Bt proteins requires substantial changes in the Bt genes, including the creation of synthetic version of the genes, rather than the microbial Bt gene itself.