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The following points highlight the top four applications of genetic engineering. The applications are: 1. Application in Agriculture 2. Application to Medicine 3. Energy Production 4. Application to Industries.
Genetic Engineering: Application # 1. Application in Agriculture:
An important application of recombinant DNA technology is to alter the genotype of crop plants to make them more productive, nutritious, rich in proteins, disease resistant, and less fertilizer consuming. Recombinant DNA technology and tissue culture techniques can produce high yielding cereals, pulses and vegetable crops.
Some plants have been genetically programmed to yield high protein grains that could show resistance to heat, moisture and diseases.
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Some plants may even develop their own fertilizers some have been genetically transformed to make their own insecticides. Through genetic engineering some varieties have been produced that could directly fix atmospheric nitrogen and thus there is no dependence on fertilizers.
Scientists have developed transgenic potato, tobacco, cotton, corn, strawberry, rape seeds that are resistant to insect pests and certain weedicides.
Bacterium, Bacillus thurenginesis produces a protein which is toxic to insects. Using the techniques of genetic engineering, the gene coding for this toxic protein called Bt gene has been isolated from bacterium and engineered into tomato and tobacco plants. Such transgenic plants showed nee to tobacco horn worms and tomato fruit worms. These genotypes are awaiting release in USA.
There are certain genetically evolved weed killers which are not specific to weeds alone but kill useful crops also. Glyphosate is a commonly used weed killer which simply inhibits a particular essential enzyme in weeds and other crop plants. A target gene of glyphosate is present in bacterium salmonella typhimurium. A mutant of S. typhimurium is resistant to glyphosate.
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The mutant gene was t cloned to E. coli and then recloned to Agrobacterium tumifaciens through its Ti Plasmid. Infection of plants with Ti plasmid containing glyphosate resistant gene has yielded crops such as cotton, tabacco maize, all of which are resistant to glyphosate.
This makes possible to spray the crop fields with glyphosate which will kill the weeds only and the genetically modified crops with resistant genes remain unaffected.
Recently Calogene, a biotech company, has isolated a bacterial gene that detoxifies; side effects of herbicides. Transgenic tobacco plants resistant to T MV mosaic virus and tomato i resistant to Golden mosaic virus have been developed by transferring virus coat protein genes »susceptible plants. These are yet to be released.
The gene transfer technology can also play significant role in producing new and improved variety of timber trees.
Several species of microorganisms have been produced that can degrade toxic chemicals and could be used for killing harmful pathogens and insect pests.
For using genetic engineering techniques for transfer of foreign genes into host plant cells, a number of genes have already been cloned and complete libraries of DNA and mt DNA of pea are now known.
Some of the cloned genes include:
(i) Genes for phaseolin of french bean,
(ii) Few phaseolin leg haemoglobin for soybean,
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(iii) Genes for small sub-unit RUBP carboxylase of pea, and i genes for storage protein in some cereals.
Efforts are being made to improve several agricultural crops using various techniques of genetic engineering which include:
(i) Transfer of nitrogen fixing genes (nif genes) from leguminous plants into cereals.
(ii) Transfer of resistance against pathogens and pests from wild plants to crop plants.
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(iii) Improvement in quality and quantity of seed proteins.
(iv) Transfer of genes for animal proteins to crop plants.
(v) Elimination of unwanted genes for susceptibility to different diseases from cytoplasmic male sterile lines in crop like maize, where cytoplasmic male sterility and susceptibility are located in mitochondrial plasmid.
(vi) Improvement of photosynthetic efficiency by reassembling nuclear and chloroplast genes and by the possible conversion of C3 plants into C4 plants.
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(vii) Development of cell lines which may produce nutritious food in bioreactors.
Genetic Engineering: Application # 2. Application to Medicine:
Genetic engineering has been gaining importance over the last few years and it will become more important in the current century as genetic diseases become more prevalent and agricultural area is reduced. Genetic engineering plays significant role in the production of medicines.
Microorganisms and plant based substances are now being manipulated to produce large amount of useful drugs, vaccines, enzymes and hormones at low costs. Genetic engineering is concerned with the study (inheritance pattern of diseases in man and collection of human genes that could provide a complete map for inheritance of healthy individuals.
Gene therapy by which healthy genes can be inserted directly into a person with malfunctioning genes is perhaps the most revolutionary and most promising aspect of genetic engineering. The use of gene therapy has been approved in more than 400 clinical trials for diseases such as cystic fibres emphysema, muscular dystrophy, adenosine deaminase deficiency.
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Gene therapy may someday be exploited to cure hereditary human diseases like haemophilia and cystic fibrosis which are caused by missing or defective genes. In one type of gene therapy new functional genes are inserted by genetically engineered viruses into the cells of people who are unable to produce certain hormones or proteins for normal body functions.
Introduction of new genes into an organism through recombinant DNA technology essentially alters protein makeup and finally i body characteristics.
Vaccines:
Recombinant DNA Technology is also used in production of vaccines against diseases. A vaccine contains a form of an infectious organism that does not cause severe disease but does cause immune system of body to form protective antibodies against infective organism. Vaccines are prepared by isolating antigen or protein present on the surface of viral particles.
When a person is vaccinate against viral disease, antigens produce antibodies that acts against the viral proteins and inactivate them. With recombinant DNA technology, scientists have been able to transfer the genes for some viral sheath proteins to vaccinia virus which was used against small pox.
Vaccines produced by gene cloning are contamination free and safe because they contain only coat proteins against which antibodies are made. A few vaccines are being produced by gene cloning, e.g., vaccines against viral hepatitis influenza, herpes simplex virus, virus induced foot and mouth disease in animals.
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Hormones:
Until recently the hormone insulin was extracted only in limited quantities from pancreas of cows and pigs. The process was not only costly but the hormone sometimes caused allergic reactions in some patients of diabetes.
The commercial production of insulin was started in 1982 through biogenetic or recombinant DNA technology and the medical use of hormone insulin was approved by food and drug administration (FDA) of USA in 1982.
The human insulin gene has been cloned in large quantities in bacterium E. coli which could be used for synthesis of insulin. Genetically engineered insulin is commercially available as humilin.
Lymphokines:
Lymphokines are proteins which regulate immune system in human body, α -Interferon is one of the examples. Interferon is used to fight viral diseases such as hepatitis, herpes, common colds as well as cancer. Such drugs can be manufactured in bacterial cell in large quantities.
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Lymphokines can also be helpful for AIDS patients. Genetically engineered interleukin-II, a substance that stimulates multiplication of lymphocytes is also available and is being currently tested on AIDS patients.
Somatostatin:
A fourteen aminoacid polypeptide hormone synthesized by hypothalamus was obtained only in a small quantity from a human cadavers. Somatostatin used as a drug for certain growth related abnormalities appears to be species specific and the polypeptide obtained from other mammals has no effect on human, hence its extraction from hypothalamus of cadavers.
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Genetic engineering technique has helped in chemical synthesis of gene which is joined to the pBR 322 plasmid DNA and cloned into a bacterium. The transformed bacterium is converted into somatostatin synthesising factory. ADA (adenosine deaminase) deficiency is a disease like combined immune deficiency which killed the bubble boy David in 1984.
The children with ADA deficiency die before they are two years old. Bone marrow cells of the child after removal from the body were invaded by a harmless virus into which ADA has been inserted.
Erythropoetin, a genetically engineered hormone is used to stimulate the production of red blood cells in people suffering from severe anaemia.
Production of Blood clotting factors:
Normally heart attack is caused when coronary arteries are blocked by cholesterol or blood clot. plasminogen is a substance found in blood clots. Genetically engineered tissue plasminogen activator (tPA) enzyme dissolves blood clots in people who have suffered heart attacks. The plasminogen activator protein is produced by genetech company which is so potent and specific that it may even arrest a heart attack underway.
Cancer:
Cancer is a dreaded disease. Antibodies cloned from a single source and targetted for a specific antigen (monoclonal antibodies) have proved very useful in cancer treatment. Monoclonal antibodies have been target with radioactive elements or cytotoxins like Ricin from castor seed to make them more deadly. Such antibodies seek cancer cells and specifically kill them with their radioactivity or toxin.
Genetic Engineering: Application # 3. Energy Production:
Recombinant DNA technology has tremendous scope in energy production. Through this technology Ii is now possible to bioengineer energy crops or biofuels that grow rapidly to yield huge biomass that used as fuel or can be processed into oils, alcohols, diesel, or other energy products.
The waste from these can be converted into methane. Genetic engineers are trying to transfer gene for cellulase to proper organisms which can be used to convert wastes like sawdust and cornstalks first to sugar and then to alcohol.
Genetic Engineering: Application # 4. Application to Industries:
Genetically designed bacteria are put into use for generating industrial chemicals. A variety of organic chemicals can be synthesised at large scale with the help of genetically engineered microorganisms. Glucose can be synthesised from sucrose with the help of enzymes obtained from genetically modified organisms.
Now-a-days with the help of genetic engineering strains of bacteria and cyanobacteria have been developed which can synthesize ammonia at large scale that can be used in manufacture of fertilisers at much cheaper costs. Microbes are being developed which will help in conversion of Cellulose to sugar and from sugar to ethanol.
Recombinant DNA technology can also be used to monitor the degradation of garbage, petroleum products, naphthalene and other industrial wastes.
For example bacterium pseudomonas fluorescens genetically altered by transfer of light producing enzyme called luciferase found in bacterium vibrio fischeri, produces light proportionate to the amount of its breaking down activity of naphthalene which provides way to monitor the efficiency of the process.
Maize and soybeans are extensively damaged by black cutworm. Pseudomonas fluorescens is found in association with maize and soybeans. Bacillus thuringiensis contain a gene pathogenic to the pest. The pest has, over the years, not only become dangerous to the crops but has developed resistance to a number of pesticides.
When the gene from B. thuringiensis (Bt) was cloned into pseudomonas fluorescence and inoculated into the soil, it was found that genetically engineered pseudomonas fluorescens could cause the death of cutworms.
