Class 12 Biology Notes Chapter 12 (Biotechnology and its Applications) – Examplar Problems Book

Detailed Notes with MCQs of Chapter 12, 'Biotechnology and its Applications'. This is a crucial chapter, not just for your board exams but also frequently tested in various government competitive exams due to its relevance in modern science and policy. We'll break down the key applications and ethical considerations.

Biotechnology and its Applications: Detailed Notes

1. Biotechnological Applications in Agriculture

• Need: To increase food production beyond the limits of the Green Revolution, reduce reliance on agrochemicals (pesticides, fertilizers), and develop crops tolerant to abiotic stresses (cold, drought, salt, heat).
• Genetically Modified Organisms (GMOs): Plants, bacteria, fungi, and animals whose genes have been altered by manipulation.
• Key Applications:
  • Pest Resistance:
    • Bt Crops: Incorporating genes from the bacterium Bacillus thuringiensis (Bt) that code for insecticidal proteins (Cry proteins).
    • Mechanism: The Bt gene codes for an inactive protoxin. When an insect ingests the plant material, the alkaline pH of its gut solubilizes the crystal and activates the toxin. The active toxin binds to the surface of midgut epithelial cells, creates pores, causing cell swelling, lysis, and eventually death of the insect.
    • Specificity: Different Bt toxins are specific to different insect groups (e.g., Lepidoptera - armyworm, Coleoptera - beetles, Diptera - flies/mosquitoes).
    • Specific Genes: cryIAc and cryIIAb control cotton bollworms; cryIAb controls corn borer.
    • Example: Bt Cotton, Bt Corn, Bt Brinjal etc.
  • Nematode Resistance (RNA Interference - RNAi):
    • Problem: Nematode Meloidogyne incognita infects roots of tobacco plants, reducing yield.
    • Mechanism (RNAi): This is a natural cellular defense mechanism in eukaryotes. It involves silencing a specific mRNA due to a complementary double-stranded RNA (dsRNA) molecule binding to it and preventing translation (silencing).
    • Application: Nematode-specific genes were introduced into the host plant (tobacco) using Agrobacterium vectors such that they produced both sense and anti-sense RNA in host cells. These two RNAs being complementary formed a dsRNA, initiating RNAi. This silenced the specific mRNA of the nematode.
    • Result: The parasite could not survive in the transgenic host expressing specific interfering RNA.
  • Nutritional Enhancement:
    • Example: Golden Rice.
    • Modification: A genetically engineered rice variety developed to produce beta-carotene (a precursor of Vitamin A). Genes from daffodil (later maize) were incorporated.
    • Purpose: To combat Vitamin A deficiency in populations heavily reliant on rice.

2. Biotechnological Applications in Medicine

• Impact: Mass production of safe and more effective therapeutic drugs. About 30 recombinant therapeutics approved worldwide (12 in India).
• Key Applications:
  • Genetically Engineered Insulin:
    • Problem: Insulin from slaughtered cattle/pigs caused allergies or immune responses in some diabetic patients.
    • Solution: Producing human insulin using recombinant DNA technology.
    • Challenge: Mature human insulin consists of two short polypeptide chains (A and B) linked by disulfide bridges. In humans, it's synthesized as pro-insulin containing an extra C-peptide, which is removed during maturation. Producing mature insulin in E. coli required separate synthesis of A and B chains and linking them.
    • Production: In 1983, Eli Lilly (an American company) prepared two DNA sequences corresponding to A and B chains, introduced them into plasmids of E. coli to produce the chains separately. These chains were extracted and combined by creating disulfide bonds to form human insulin (Humulin).
  • Gene Therapy:
    • Definition: Collection of methods allowing correction of a gene defect diagnosed in a child/embryo. Involves delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene.
    • First Clinical Case (1990): A 4-year-old girl with Adenosine Deaminase (ADA) deficiency. This enzyme is crucial for immune system function. Deficiency leads to Severe Combined Immunodeficiency (SCID).
    • Treatment Approaches:
      • Bone marrow transplantation (requires suitable donor).
      • Enzyme replacement therapy (requires regular injections).
      • Gene Therapy Approach: Lymphocytes from the patient's blood are grown in culture. A functional ADA cDNA (using a retroviral vector) is introduced into these lymphocytes. These genetically engineered lymphocytes are returned to the patient.
      • Limitation: These cells are not immortal; periodic infusion is needed. If the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.
    • Types: Somatic cell gene therapy (targets body cells, not heritable) and Germline gene therapy (targets sperm/egg/zygote, heritable, currently not ethical/legal).
  • Molecular Diagnostics:
    • Need: Early diagnosis is crucial for effective treatment. Conventional methods (serum/urine analysis) often detect diseases too late.
    • Recombinant DNA Technology Based Methods:
      • PCR (Polymerase Chain Reaction): Can detect very low concentrations of bacteria/viruses by amplifying their nucleic acid. Used to detect HIV in suspected AIDS patients (detects viral RNA/DNA before antibodies appear), detect gene mutations in suspected cancer patients, and in many other genetic disorders.
      • ELISA (Enzyme-Linked Immunosorbent Assay): Based on the principle of antigen-antibody interaction. Infection by a pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting antibodies synthesized against the pathogen.
      • Autoradiography (using Probes): 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. The clone having the mutated gene will not appear on the photographic film because the probe will not have complementarity with the mutated gene. Used to detect specific genetic mutations (e.g., cancer, cystic fibrosis).

3. Transgenic Animals

• Definition: Animals that have had their DNA manipulated to possess and express an extra (foreign) gene. Over 95% are mice.
• Reasons for Creation:
  • Normal Physiology and Development: Study how genes are regulated and affect normal body functions and development (e.g., study complex factors like insulin-like growth factor).
  • Study of Disease: Serve as models for human diseases to understand disease development and test new treatments (e.g., models for cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's).
  • Biological Products: Produce useful biological products. Transgenic animals are created that produce the product in their milk, blood, or urine.
    • Examples: Human protein alpha-1-antitrypsin used to treat emphysema. Rosie, the first transgenic cow (1997), produced human protein-enriched milk (2.4 g/L) containing human alpha-lactalbumin, nutritionally more balanced for human babies.
  • Vaccine Safety: Used to test the safety of vaccines before human trials (e.g., transgenic mice for polio vaccine safety).
  • Chemical Safety Testing (Toxicity Testing): Transgenic animals made more sensitive to toxic substances can provide results in less time compared to non-transgenic animals.

4. Ethical Issues

• Manipulation of living organisms raises ethical questions. Unpredictable results when GMOs are introduced into the ecosystem.
• Bioethics: Standards required to evaluate the morality of human activities that might help or harm living organisms.
• GEAC (Genetic Engineering Approval Committee): An Indian government organization set up to make decisions regarding the validity of GM research and the safety of introducing GM organisms for public services.
• Biopiracy: The term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned and without compensatory payment.
  • Developed nations are often rich in technology but poor in biodiversity, while developing nations are rich in biodiversity and traditional knowledge.
  • Examples: Basmati rice (US patent on a variety derived from Indian farmer's varieties), Turmeric, Neem.
  • Counteraction: Indian Parliament has cleared the second amendment of the Indian Patents Bill, considering issues like patent terms, emergency provisions, and research/development initiatives.

Multiple Choice Questions (MCQs)

1. The Cry proteins produced by Bacillus thuringiensis are toxic to insects primarily because:
   a) They directly inhibit DNA replication in insect cells.
   b) They become active in the acidic pH of the insect foregut.
   c) They bind to midgut epithelial cells and create pores after activation in alkaline pH.
   d) They interfere with the insect's nervous system transmission.

2. RNA interference (RNAi) used to develop pest resistance in tobacco plants targets which specific molecule of the nematode Meloidogyne incognita?
   a) Ribosomal RNA (rRNA)
   b) Transfer RNA (tRNA)
   c) Specific messenger RNA (mRNA)
   d) DNA polymerase

3. Golden Rice, a genetically modified crop, is enriched with which nutrient precursor?
   a) Vitamin C
   b) Folic Acid
   c) Beta-carotene (Pro-vitamin A)
   d) Iron

4. The production of genetically engineered human insulin (Humulin) by Eli Lilly involved:
   a) Direct extraction from human pancreas.
   b) Synthesizing A and B polypeptide chains separately in E. coli and joining them.
   c) Using pig insulin modified chemically.
   d) Culturing human pancreatic cells in vitro.

5. The first clinical gene therapy was performed in 1990 to treat a deficiency of which enzyme?
   a) DNA Ligase
   b) Restriction Endonuclease
   c) Adenosine Deaminase (ADA)
   d) Tyrosinase

6. Which molecular diagnostic technique is highly effective for detecting very low concentrations of a pathogen like HIV, especially in the early stages of infection?
   a) ELISA
   b) Autoradiography
   c) Polymerase Chain Reaction (PCR)
   d) Serum analysis

7. The diagnostic principle of ELISA is based on:
   a) Nucleic acid amplification
   b) Antigen-antibody interaction
   c) DNA hybridization using probes
   d) Analysis of metabolic products

8. The transgenic cow 'Rosie' was developed to produce milk enriched with:
   a) Alpha-1-antitrypsin
   b) Human alpha-lactalbumin
   c) Insulin
   d) Interferon

9. Which organization in India is responsible for evaluating the safety and validity of GM research and products for public use?
   a) ICMR (Indian Council of Medical Research)
   b) CSIR (Council of Scientific and Industrial Research)
   c) DBT (Department of Biotechnology)
   d) GEAC (Genetic Engineering Approval Committee)

10. The term 'Biopiracy' refers to:
    a) The illegal hunting of endangered species for biological products.
    b) The unauthorized use of bio-resources and traditional knowledge without proper compensation.
    c) The accidental release of genetically modified organisms into the environment.
    d) The patenting of genetically modified organisms by government labs.

Answer Key:

1. c
2. c
3. c
4. b
5. c
6. c
7. b
8. b
9. d
10. b

Study these notes thoroughly. Remember the specific examples, mechanisms (like Bt toxin action, RNAi), key applications, and the role of regulatory bodies like GEAC. Good luck with your preparation!