Biotechnology and Its Applications Biology Notes - GM Crops, Bt Cotton, RNAi, Insulin, Gene Therapy, Transgenic Animals and Bioethics

Biotechnology has many applications such as biopharmaceuticals, therapeutics, diagnostics, genetically modified crops, processed food, bioremediation, waste treatment, and energy production.

Biotechnology has 3 Critical Research Areas:

1. Providing the best catalyst in the form of an improved organism, usually a microbe or enzyme.
2. Creating optimal conditions through engineering for a catalyst to act.
3. Downstream processing technologies to purify the protein/organic compound.

Applications in Agriculture

3 Options for Increasing Food Production

1. Agro-chemical based agriculture: Uses fertilizers and pesticides. Expensive and causes environmental pollution.
2. Organic agriculture: Expensive.
3. Genetically engineered crop-based agriculture: Uses genetically modified crops. Genetically Modified Organisms (GMO) are plants, bacteria, fungi, and animals whose genes are altered by manipulation.

Advantages of Genetic Modification in Plants

• Makes crops more tolerant to abiotic stresses (cold, drought, salt, heat, etc.).
• Pest-resistant crops reduce the use of chemical pesticides.
• Reduces post-harvest losses.
• Increases efficiency of mineral usage by plants, preventing early exhaustion of soil fertility.
• Enhances nutritional value of food, e.g., Golden rice (Vitamin A-enriched rice).
• Creates tailor-made plants to supply alternative resources (starches, fuels, pharmaceuticals, etc.) to industries.

Pest Resistant Plants

• Act as bio-pesticides.
• Reduce the need for insecticides.
• Examples: Bt cotton, Bt corn, rice, tomato, potato, soybean, etc.

Bt Cotton

• Some strains of Bacillus thuringiensis have proteins that kill insects like coleopterans (beetles), lepidopterans (tobacco budworm, armyworm), and dipterans (flies, mosquitoes).
• B. thuringiensis forms an insecticidal protein (Bt toxin) crystal during a phase of their growth. It does not kill the Bacillus as it exists as inactive protoxins.
• When an insect ingests the toxin, it becomes active due to the alkaline pH of the gut, which solubilizes the crystals. The toxin binds to the surface of mid-gut epithelial cells, creating pores, causing cell swelling, lysis, and death of the insect.
• Bt toxin genes were isolated from B. thuringiensis and incorporated into crop plants such as cotton.
• Most Bt toxins are insect-group specific, coded by cry genes. For example, proteins encoded by cryIAc and cryIIAb genes control cotton bollworms, while the protein of cryIAb gene controls corn borer.

Nematode Resistance in Tobacco Plants

• A nematode, Meloidogyne incognita, infects the roots of tobacco plants, causing a reduction in yield.
• It can be prevented by RNA interference (RNAi) strategy.
• RNAi is a method of cellular defense in all eukaryotic organisms. It prevents translation of a specific mRNA (silencing) due to a complementary dsRNA molecule.
• The source of this complementary RNA is from an infection by RNA viruses or mobile genetic elements (transposons) that replicate via an RNA intermediate.
• Isolate nematode-specific genes (DNA) and introduce them into the host plant using Agrobacterium vectors. This produces both sense and anti-sense RNA in host cells, which are complementary, forming double-stranded (ds) RNA. This initiates RNAi, silencing the specific mRNA of the nematode, preventing the parasite from surviving in the transgenic host expressing specific interfering RNA.

Applications in Medicine

• Recombinant DNA technology helps for mass production of safe and more effective therapeutic drugs.
• Products from non-human sources cause unwanted immunological responses, but recombinant therapeutics do not have such problems.
• At present, about 30 recombinant therapeutics have been approved, of which 12 are being marketed in India.

1. Genetically Engineered Insulin

• Insulin is used to manage adult-onset diabetes.
• Insulin from the pancreas of animals (cattle and pigs) causes allergy or other types of reactions to the foreign protein.
• Now, it is possible to produce human insulin using bacteria.
• Insulin consists of two short polypeptide chains (chain A and chain B) that are linked by disulfide bridges.
• In mammals, insulin is synthesized as a pro-hormone (pro-insulin). It is processed to become a mature and functional hormone.

• The pro-hormone contains an extra stretch called C peptide, which is removed during maturation into insulin.
• In 1983, Eli Lilly (an American company) prepared two DNA sequences corresponding to A and B chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were combined by creating disulfide bonds to form human insulin (Humulin).

2. Gene Therapy

• It is a method to correct a gene defect in a child/embryo.
• Genes are inserted into a person’s cells and tissues to treat a hereditary disease, compensating for the non-functional gene.
• The first clinical gene therapy (1990) was given to a 4-year-old girl with adenosine deaminase (ADA) deficiency.
• This is caused due to the deletion of a gene of adenosine deaminase (an enzyme for the functioning of the immune system). It can be cured by bone marrow transplantation or by enzyme replacement therapy (injection of ADA), but these are not completely curative.
• Gene therapy for ADA deficiency: Collect lymphocytes from the patient’s blood and grow in a culture, introduce a functional ADA cDNA into lymphocytes (using a retroviral vector), and return them to the patient.
• This should be periodically repeated as lymphocytes are not immortal.
• If the ADA gene from marrow cells is introduced into cells at early embryonic stages, it could be a permanent cure.

3. Molecular Diagnosis

• Conventional methods (serum and urine analysis) are not suitable for early diagnosis of diseases.
• It is possible by techniques such as Recombinant DNA technology, PCR, and ELISA.

PCR (Polymerase Chain Reaction)

• Presence of a pathogen is normally suspected only based on symptoms. By this time, the concentration of pathogen is already very high in the body.
• Very low concentration of a bacteria or virus can be detected by amplification of their nucleic acid by PCR.
• Uses of PCR:
  • To detect HIV in suspected patients.
  • To detect gene mutations in suspected cancer patients.
  • To identify many other genetic disorders.
• A single-stranded DNA or RNA, tagged with a radioactive molecule (probe), is hybridized to its complementary DNA in a clone of cells. It is detected by autoradiography. The clone having a mutated gene will not appear on photographic film because the probe will not have complementarity with the mutated gene.

ELISA (Enzyme Linked Immuno-Sorbent Assay)

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

Transgenic Animals

• These are animals whose genome has been altered by the introduction of a foreign gene by manipulation.
• Examples include transgenic rats, rabbits, pigs, sheep, cows, and fish.
• Over 95% of transgenic animals are mice.

Benefits of Transgenic Animals

• To study regulation of genes and their action on normal physiology and development: For example, study of insulin-like growth factor. Genes (from other species) that alter the formation of this factor are introduced, and the biological effects are studied. This provides information about the biological role of the factor.
• To study the contribution of genes in the development of a disease and thereby new treatments: For example, transgenic models for human diseases such as cancer, cystic fibrosis, rheumatoid arthritis, and Alzheimer’s.
• Biological products: Some medicines contain expensive biological products. Transgenic animals can be used to produce biological products by introducing genes that code for a particular product.

They are used to treat diseases such as emphysema, phenylketonuria (PKU), and cystic fibrosis. For example, human protein (α-1-antitrypsin) is used to treat emphysema.

In 1997, Rosie (the first transgenic cow) produced human protein-enriched milk (2.4 gm per litre). It contains human α-lactalbumin, a nutritionally more balanced product for human babies than natural cow-milk.

• Vaccine safety testing: Transgenic mice are used to test the safety of the polio vaccine. If reliable, they can replace the use of monkeys to test the safety of vaccines.
• Chemical safety testing (toxicity testing): Some transgenic animals carry genes that make them more sensitive to toxic substances than non-transgenic animals. They are exposed to toxic substances, and the effects are studied, giving immediate results.

Ethical Issues

• Problem of unpredictable results: Genetic modification may cause unpredictable results.

The Indian Government has set up organizations like GEAC (Genetic Engineering Approval Committee) to make decisions about the validity of GM research and the safety of GM organisms for public services.

• Bio-piracy: This is the use of bio-resources by multinational companies and other organizations without proper authorization from the countries and people concerned. Certain companies have obtained patents for products and technologies that make use of genetic materials, plants, etc., that have been identified, developed, and used by farmers and indigenous people of a country. For example, Basmati rice, herbal medicines (turmeric, neem, etc.).

Basmati rice has a unique aroma and flavor. India has 27 varieties of Basmati. In 1997, an American company obtained patent rights on Basmati rice through the US Patent and Trademark Office. This allowed the company to sell a ‘new’ variety of Basmati, which was actually derived from Indian farmer’s varieties. Indian Basmati was crossed with semi-dwarf varieties and claimed as a novelty. Other people selling Basmati rice could be restricted by the patent.

Generally, industrialized nations are poor in biodiversity and traditional knowledge, while the developing and underdeveloped world has rich biodiversity and traditional knowledge related to bio-resources.

It is necessary to develop laws to prevent unauthorized exploitation of bio-resources and traditional knowledge.

The Indian Parliament has cleared the second amendment of the Indian Patents Bill, which considers patent terms, emergency provisions, and research and development initiatives.