Transgenic Animals & Plants | Biology Class 12 - NEET PDF Download

Transgenic Animals

Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals. Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced, although over 95 percent of all existing transgenic animals are mice.

Application of Transgenic Animals

(i) Normal Physiology and Development : Transgenic animals can be specifically designed to allow the study of how genes are regulated, and how they affect the normal functions of the body and its development, e.g., study of complex factors involved in growth such as insulin-like growth factor. By introducing genes from other species that alter the formation of this factor and studying the biological effects that result, information is obtained about the biological role of the factor in the body.

(ii) Study of Disease : Many transgenic animals are designed to increase our understanding of how genes contribute to the development of disease. These are specially made to serve as models for human diseases so that investigation of new treatments for diseases is made possible. Today transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's

(iii) Biological products : Medicines required to treat certain human diseases can contain biological products, but such products are often expensive to make. Transgenic animals that produce useful biological products can be created by the introduction of the portion  of DNA (or genes) which codes for a particular product such as human protein (a-1-antitrypsin) used to treat emphysema. Similar attempts are being made for treatment of phenylketonuria (PKU) and cystic fibrosis. In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre). The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies that natural cow-milk.

(iv) Vaccine safety : Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine. If successful and found to be reliable, they could replace the use of monkeys to test the safety of batches of the vaccine.

(v) Chemical Safety Testing : This is known as toxicity/safety testing. The procedure is the same as that used for testing toxicity of drugs. Transgenic animals are made that carry genes which make them more sensitive to toxic substances than non-transgenic animals. They are then exposed to the toxic substances and the effects studied. Toxicity testing in such animals will allow us to obtain results in less time.

Transgenic Plants

Application of Transgenic Plants

1. They have proved to be extremely valuable tools in studies on plant molecular biology, regulation of gene action, identification of regulatory promontory sequences etc.

2. Specific genes have been transferred into plants to improve their agronomic and other features.

3. Genes for resistance to various biotic stresses have been engineered to generate transgenic plants resistant to insects viruses etc. 

4. Several gene transfers have been aimed at improving the produce quality e.g., protein or lipid quality etc. of transgenic plants ;

5. Transgenic plants are aimed to produce novel biochemicals like interferon, insulin, immunoglobulins etc.,

6. Transgenic plants have been produced that express a gene encoding an antigenic protein from a pathogen.

7. Made crops more tolerant to  abiotic stresses (cold, drought, salt, heat).

8. Reduced reliance on chemical pesticides (pest-resistant crops).

9. Helped to reduce post harvest losses.

10. Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).

11. Enhanced nutritional value of food e.g., Vitamin 'A' enriched rice.

Genetic Modified Food

 The food is prepared from genetically modified crop[transgenic] is called genetically modified food or GM Food.

GM food differs from the food prepared from the produce of conventionally developed varieties mainly in the following aspects. Firstly, it contains the protein produced by the trangene in question, e.g., Cry protein in the case of insect resistant varieties. Secondly,it contains the enzyme produced by the antibiotic resistance gene that was used during gene transfer by genetic engineering. Finally, it contains the antibiotic resistance gene itself.

GM foods could lead to the following problems when they are consumed. Firstly, the transgene product may toxicity and or produce allergies. Secondly, the enzyme produced by the antibiotic resistance gene could cause allergies, since it is a foreign protein. Finally, the bacteria present in the alimentary canal of the humans could take up the antibiotic resistance gene that is present in the GM food.

Biochemical Production

Plants are the chief source carbohydrates, e.g., starch, sugar etc., lipids, proteins, and a variety of unique biochemicals. Transgenes have been shown to introduce novel branches in the biosynthetic pathways of plants and, thereby, to generate valuable products or to produce new, valuable proteins virtually all the cases are promising and in developmental stages, except for the thrombin inhibitor protein hirudin, which is the first commercial example - Hirudin.

Old NCERT Syllabus

Bio-Pesticides 

Bio-pesticides are those biological agents that are used for control of weeds, insects and  pathogens. The micro-organisms used as bio-pesticides include viruses, bacteria, fungi, protozoa and mites.

One example is the soil bacterium, Bacillus thuringiensis. Spores of this bacterium produce the insecticidal Cry protein. Therefore, spores of this bacterium kill larvae of certain insects. The commercial preparations of B. thuringiensis contain a mixture of spores, Cry protein and an inert carrier. This bacterium was the first bio-pesticide to be used on a commercial scale in the world.

The very familiar beetle with red and black markings-the Ladybird, and Dragonflies are useful to get rid of aphids and mosquitoes, respectively. An example of microbial bio-control agents that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis (often written as Bt). These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed. The bacterial disease will kill the caterpillars, but leave other insects unharmed.

Fungal pathogens are attractive bio-control agents for weed control in view of their host specificity and ease in production and inoculation in the field where, A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma.
Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective bio-control agents of several plant pathogens.

Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal application. They have been shown to have no negative impacts on plants, mammals, birds, fish or even on non-target insects. This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is being treated.  

Between bio-pesticides and chemical pesticides

Biofertilisers

Bio-fertilisers are organisms that enrich the nutrient quality (N,P) of the soil. The main sources of bio-fertilisers are bacteria, fungi and cyanobacteria.

Bacteria Rhizobium (symbiotic bacteria) fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient.
Other bacteria like Azospirillum and c Azotobacter can fix atmospheric nitrogen while free-living in the soil thus enriching the nitrogen content of the soil.

Fungi are also known to form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza.
Fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant. Also provide resistance to root-borne pathogens, tolerance to salinity and drought and cause an overall increase in plant growth and development.

Cyanobacteria are autotropic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen. (e.g. Anabaena, Nostoc, Oscillatoria, etc.) In paddy fields, cyanobacteria serve as an important bio-fertiliser. Blue green algae also add organic matter to the soil and increase its fertility.

Bio-fertilisers are a low-cost input and they do not pollute the environment. They are use to replenish soil nutrients. They also reduce the dependence on chemical fertilisers and also help to use organic farming.