Chapter 10: Biotechnology and its Applications
Introduction
Biotechnology essentially deals with industrial-scale production of biopharmaceuticals and biologicals using genetically modified microbes, fungi, plants, and animals. The applications of biotechnology include therapeutics, diagnostics, genetically modified crops for agriculture, processed food, bioremediation, waste treatment, and energy production.
Biotechnological Applications in Agriculture
To increase food production, there are three options:
- Agro-chemical based agriculture
- Organic agriculture
- Genetically engineered crop-based agriculture
Plants, bacteria, fungi, and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMOs). GM plants have been useful in many ways:
- Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
- Reduced reliance on chemical pesticides (pest-resistant crops).
- Helped to reduce post-harvest losses.
- Increased efficiency of mineral usage by plants.
- Enhanced nutritional value of food, e.g., golden rice, i.e., Vitamin ‘A’ enriched rice.
Bt Cotton
Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans, coleopterans, and dipterans. B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. Why does this toxin not kill the Bacillus? Because the Bt toxin protein exists as inactive protoxins. Once an insect ingests the inactive toxin, it is converted into an active form due to the alkaline pH of the gut which solubilises the crystals. The activated toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis, leading to death. Specific Bt toxin genes (e.g., cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer) were isolated and incorporated into crops.
Pest Resistant Plants (RNA Interference)
A nematode Meloidegyne incognita infects the roots of tobacco plants. A novel strategy was adopted based on the process of RNA interference (RNAi). RNAi takes place in all eukaryotic organisms as a method of cellular defense. It involves silencing a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).
Biotechnological Applications in Medicine
Genetically Engineered Insulin
Management of adult-onset diabetes is possible by taking insulin. Earlier, insulin was extracted from pancreas of slaughtered cattle and pigs. Human insulin consists of two short polypeptide chains: chain A and chain B, linked together by disulphide bridges. In mammals, insulin is synthesized as a pro-hormone (containing an extra stretch called the C peptide), which is removed during maturation. The main challenge for commercial production using rDNA techniques was getting insulin assembled into a mature form. 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 produced separately, extracted, combined by creating disulfide bonds to form human insulin (Humulin).
Gene Therapy
If a person is born with a hereditary disease, gene therapy is an attempt to correct it. It involves delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene. The first clinical gene therapy was given in 1990 to a 4-year-old girl with Adenosine deaminase (ADA) deficiency. ADA is crucial for the immune system to function. The disorder is caused by the deletion of the gene for ADA. As a cure, lymphocytes from the patient’s blood are grown in culture, and a functional ADA cDNA (using a retroviral vector) is introduced and returned to the patient. Since these cells are not immortal, the patient requires periodic infusions unless the gene is isolated from marrow cells and introduced at early embryonic stages (a permanent cure).
Molecular Diagnosis
Early detection is required for effective disease treatment. Conventional methods (serum and urine analysis) do not yield early detection.
- PCR (Polymerase Chain Reaction): Amplifies nucleic acid. Can detect very low concentrations of a bacteria or virus (like HIV or mutations in cancer genes).
- ELISA: Used to detect antigen-antibody reactions.
- Autoradiography: A single-stranded DNA or RNA tagged with a radioactive molecule (probe) is allowed to hybridize to its complementary DNA in a clone of cells followed by detection using autoradiography. Mutated genes will not appear on the photographic film.
Transgenic Animals
Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals. Currently, most are transgenic mice (about 95%). Reasons for producing them:
- Normal physiology and development: To study how genes are regulated (e.g., studying insulin-like growth factors).
- Study of disease: Serve as models for human diseases like cancer, cystic fibrosis, rheumatoid arthritis, and Alzheimer’s.
- Biological products: To produce useful biological products (e.g., human protein \(\alpha\)-1-antitrypsin for treating emphysema). In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre).
- Vaccine safety: Testing safety of vaccines (e.g., polio vaccine on transgenic mice).
- Chemical safety testing: Toxicity testing using animals made more sensitive to toxic substances.
Ethical Issues and Biopiracy
The Indian Government has set up organizations such as GEAC (Genetic Engineering Approval Committee) to make decisions regarding the validity of GM research and the safety of introducing GM-organisms for public services.
Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organizations without proper authorization from the countries and people concerned without compensatory payment. Examples include foreign patents on distinct Indian varieties of Basmati rice, Neem, and Turmeric.
Competency Based Questions
Q1. Describe mechanically why the potentially lethal cryIAc endotoxin protein produced by Bacillus thuringiensis completely fails to destroy the bacterium itself during its crystalline growth phase, yet rapidly kills a target bollworm larva upon ingestion.
Answer and Explanation
Answer: The protoxin requires an alkaline pH to dissolve and become active.Explanation:
The Bacillus thuringiensis bacterium safely synthesizes the extremely toxic cry endotoxin primarily because it is initially produced and stored inside the bacterial cell as an inactive crystallized precursor called a protoxin.
When a target bollworm larva severely infests a Bt-crop and indiscriminately ingests the tissues containing these crystals, the protoxin quickly reaches the larva’s midgut. Crucially, the insect’s midgut environment possesses a highly alkaline pH. This specific high pH violently solubilizes the inert crystal lattice, enzymatically cleaving the precursor and converting it into a lethal, active toxin. The active toxin then physically binds to specific receptor proteins exclusively located on the exposed surface of the midgut epithelial cells, creating gaping pores that force massive cellular swelling and eventual lysis, killing the insect.
Q2. An engineer artificially attempts to coax a simple transformed E. coli culture to directly translate an un-edited full-length human genomic DNA sequence coding absolutely for insulin. Based on Eli Lilly’s 1983 findings, explain why this initial naive attempt will fail to yield biochemically functional, mature Human Insulin molecules for pharmaceutical use.
Answer and Explanation
Answer: Bacteria lack enzymes to remove the C-peptide and form the precise disulfide bridges automatically.Explanation:
In humans, insulin is genetically translated initially as a single long, continuous polypeptide pro-hormone consisting of an A-chain, a central linking C-peptide chain, and a B-chain. Crucially, for insulin to become a biochemically active, mature hormone, the intervening C-peptide sequence must be enzymatically excised perfectly, and the remaining A and B chains must be precisely linked together via delicate intermolecular disulfide bridges.
Prokaryotes like E. coli simply do not possess the sophisticated eukaryotic post-translational modification enzymatic machinery required to selectively snip out the C-peptide and catalyze those exact disulfide linkages. Consequently, the bacteria would just hopelessly produce biologically inert, hopelessly misfolded pro-insulin.
Eli Lilly elegantly solved this by completely synthesizing two separate, distinct DNA genes tailored exactly for the A and B chains, growing them separately in entirely different E. coli vats, extracting the naked chains, and then chemically inducing the correct disulfide bonds in vitro to synthesize pure, mature ‘Humulin’.
Q3. If a novel viral infection was suspected perfectly within a completely asymptomatic patient exhibiting extremely heavily depressed pathogen loads below standard clinical detection thresholds, mathematically justify why Polymerase Chain Reaction (PCR) serves as the superior definitive molecular diagnostic tool over traditional serological ELISA tests for this specific window period.
Answer and Explanation
Answer: PCR provides an exponential geometric amplification of viral templates (\(N_0 \times 2^n\)), overcoming low thresholds directly.Explanation:
Traditional diagnostic techniques like direct serum analysis or pathogen culturing require a relatively substantial physical concentration of the pathogen or its symptomatic toxins to register a positive visual hit. Even an ELISA relies on the immune system having sufficient time to produce copious macroscopic amounts of specific antibodies, which entirely fails during an early asymptomatic “window” period when antigen or antibody liters are below detection.
PCR completely circumvents all minimum biological threshold limits. If even one single solitary microscopic viral DNA/RNA template molecule (\(N_0 = 1\)) is present anywhere in the extracted fluid, the automated PCR thermal cycling process will mathematically force standard exponential geometric magnification (\(1 \to 2 \to 4 \to 8 \to 16 \dots\)). According to the equation \(N_f = N_0(2)^n\), after just 30 standard cycles, that single undetectable molecule is amplified over roughly \(1 \times (2^{30}) \approx 1,000,000,000\) (one billion) times. This explosive, mathematically guaranteed amplification turns an invisible trace pathogen load into a massively dense, easily scorable DNA band directly confirming the active presence of the virus before standard antibodies ever form.
Q4. A multinational pharmaceutical corporation secretly discovers and successfully patents a completely unique, naturally occurring, infection-resistant genetic trait found exclusively functioning within an indigenous, historically cultivated Indian turmeric strain without compensating local farmers or acknowledging origins. Categorize this specific legal/ethical offense using recognized international terminology, and name the specific protective Indian government committee mandated to intercept such acts.
Answer and Explanation
Answer: Biopiracy; GEAC (Genetic Engineering Approval Committee).Explanation:
The described unethical action represents a textbook case of Biopiracy. Biopiracy is distinctly defined as the systemic exploitation, appropriation, and commercial patent sealing of natural bio-resources, native genetic traits, or traditional historical knowledge tightly associated with culturally indigenous populations by massive multinational organizations without giving proper legal authorization, formal acknowledgment, or proportional compensatory financial payment to the sovereign countries or local people originally stewarding the resources.
In India, the primary national regulatory body strictly mandated to legally oversee, validate, and authorize all major genetic engineering research, patent approvals involving Indian bio-resources, and large-scale public safety matters regarding GMOs is the Genetic Engineering Approval Committee (GEAC).
Q5. Contrast the fundamental operational mechanism by which a normal agricultural pesticide conventionally kills a crop-destroying nematode versus the highly targeted cellular method of RNA interference (RNAi) utilized by advanced transgenic tobacco plants.
Answer and Explanation
Answer: Pesticides are broad-spectrum chemical contact poisons; RNAi selectively silences specific vital mRNA translation.Explanation:
Conventional agricultural nematodes are usually eradicated using toxic chemical nematicides/pesticides applied heavily across the soil. These act as extremely broad-spectrum, crude contact poisons that indiscriminately disrupt basic universal physiological functions (like generalized nervous system synapses or basic cellular respiration) across all exposed organisms indiscriminately, often causing massive ecological collateral damage.
In stark contrast, advanced GMO tobacco plants employ RNA interference (RNAi) as a highly elegant, microscopic, and laser-targeted endogenous cellular defense strategy. When the Meloidegyne incognita nematode actively burrows into and feeds upon the transgenic tobacco roots, it unwittingly ingests highly specific double-stranded RNA (dsRNA) engineered by the plant. Inside the nematode’s cells, this dsRNA perfectly physically matches and forcibly binds completely selectively to a complementary strand of a specifically targeted crucial nematode messenger RNA (mRNA) required for its survival. This perfectly matched binding actively blocks the host ribosomes, physically preventing the actual translation of that one specific vital protein—a phenomenon termed “silencing.” Deprived of that specific essential protein exclusively, the targeted parasite starves and dies without dumping generalized toxic chemicals into the broader agricultural ecosystem.