APPLICATIONS OF BIOTECHNOLOGY

Learning Goals:


Three critical research areas of biotechnology are as follows:



BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE

Following are the three options that can be utilized for increasing food production:

  1. Agro-chemical based agriculture
  2. Organic agriculture
  3. Genetically engineered crop-based agriculture

The Green Revolution helped in significantly improving the food supply. It has caused much harm to the environment; in the form of groundwater depletion, soil pollution and water pollution. Organic farming is environment friendly but has failed to keep pace with the growing need of human population.

Genetically Modified Organisms: Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO).

Following are some of the benefits of genetic modification of plants:

Bt Toxin: It is produced by a bacterium called Bacillus thuringiensis. Bt toxin gene has been cloned from the bacteria and has been expressed in plants; in order to provide resistance to insects. This has helped in ruling out the need for insecticides. Examples of plants with Bt toxin gene are; Bt cotton, Bt corn, rice, tomato, potato, soyabean, etc.

Bt Cotton: Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. The Bt toxin protein exists as inactive protoxin in B. thuringiensis. Once, an insects ingests the inactive toxin, the alkaline pH of the gut solubilise the crystals and makes the toxin active. The activated toxin binds to the surface of midgut epithelial cells and creates pores. These pores cause swelling and lysis and eventually result in death of the insect. Since most Bt toxins are insect-group specific, hence choice of genes depends upon the crop and the targeted pest. Some of the proteins encoded by the genes are cryIAc, cryIIAb and cryIAb.

Pest Resistant Plants: Many nematodes live as parasite on a wide variety of plants and animals; including human beings. Let us take the example of the nematode Meloidegyne incognitia. This nematode infects the roots of tobacco plants and causes huge loss in yield. Prevention of this infestation is based on the process of RNA interference (RNAi). RNAi takes place in all organisms as a method of cellular defense. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA. The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate.

Nematode specific genes were introduced into the host plant; by using Agrobacterium vectors. The introduction of DNA produced both sense and anti-sense RNA in the host cells. These two RNAs (being complementary to each other) formed a double stranded (dsRNA). The dsRNA initiated RNAi and thus silenced the specific mRNA of the nematode. As a result; the parasite could not survive in a transgenic host.


BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE

Genetically Engineered Insulin

Many patients of diabetes need to take insulin on a regular basis. Insulin can be made from human sources but that will not be enough to meet the demand of an ever growing population of diabetic patients. Insulin from animal sources can create many problems for the patient who is taking insulin. If a bacterium could be manipulated to produce insulin, it can solve the problem of quantity as well as quality.

Insulin consists of two short polypeptide chains, viz. chain A and chain B. The two chains are linked together by disulphide bridges. In mammals, insulin is synthesized as a pro-hormone which contains an extra stretch called C-peptide. This C-peptide is not present in mature insulin. Assembling the insulin into a mature form was the main challenge.

In 1983, an American company named Eli Lilly prepared two DNA sequences corresponding to A and B chains of human insulin. These sequences were introduced into plasmids of E. coli to produce insulin chains. Chains A and B were produced separately. They were extracted and combined by creating disulphide bonds to form human insulin.

Gene Therapy

Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. Correction of a genetic defect involves delivery of a normal gene into the individual or embryo. The normal gene takes over the function of and compensates for the non-functional gene.

ADA Deficiency: The first clinical gene therapy was given in 1990 to a 4-year old girl who was suffering from adenosine deaminase (ADA) deficiency. This enzyme is crucial for proper functioning of the immune system. This disorder is caused due to the deletion of the gene for ADA.

Conventional treatment of ADA deficiency is through bone marrow transplantation or through enzyme replacement therapy. But these methods do not ensure complete cure.

The first step towards gene therapy involves taking lymphocytes from the blood of the patient and growing them in a culture. Then a functional ADA cDNA (using a retroviral vector) is introduced into these lymphocytes. The lymphocytes are then returned to the patient’s body. Since lymphocytes die after some time, the patient needs periodic infusion of genetically modified lymphocytes. But if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.

Molecular Diagnosis

Conventional methods of diagnosis involves analysis of serum, urine, etc. But these methods cannot ensure early diagnosis. Early diagnosis helps in much better way to treat a disease. The techniques which help in early diagnosis are; Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA).

Even very low concentration of a pathogen can be detected by amplification of their nucleic acid by PCR. This method is now routinely used to detect HIV in suspected AIDS patients.

ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.


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. Transgenic animals provide following advantages:

  1. Normal physiology and development: Transgenic animals can be specifically designed to allow the study of how genes are regulated. They are designed to allow study of how genes affect the normal functions of the body and its development.
  2. Study of disease: Transgenic animals can be designed to increase our understanding of the role of genes in development of disease.
  3. Biological products: Some medicines contain biological products. It is very expensive to make such products. Transgenic animals can be designed to produce useful biological products. This can be done by introducing the gene which codes for a particular molecule.
  4. Vaccine safety: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. This helps in stopping cruelty to animals to a large extent.
  5. Chemical safety testing: 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. This helps in obtaining the results in less time.

ETHICAL ISSUES

Manipulation of living organisms by the human race can go out of hand if not checked. Moreover, introduction of a genetically modified organism in the ecosystem can have unpredictable consequences. This too needs to be kept in check. The Indian Government has set up GEAC (Genetic Engineering Approval Committee). This organization makes decisions regarding the validity and safety of GM research.

Biopiracy: The use of bio-resources by MNCs and other organizations without proper authorization from countries and people concerned; without compensatory payment is called biopiracy.

There has been many cases in which companies and/or people from developed nations have obtained patent rights on novel uses of bioresources which had been part of the traditional knowledge of developing countries. Patent on a new variety of Basmati rice by an American is one such example.


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