class 12 notes

Class 12 Biology Notes Chapter 12 (Biotechnology and its applications) – Biology Book

Philoid

Philoid

— 7 min read

Biology
Alright class, let's delve into Chapter 12: Biotechnology and its Applications. We've already learned the tools and techniques in the previous chapter; now we'll see how these powerful tools are being used to improve human life in various fields, particularly agriculture and medicine. Remember, this chapter is crucial not just for your board exams but also for various competitive government exams where applied biology questions are common.

Chapter 12: Biotechnology and its Applications - Detailed Notes

I. Introduction

  • Biotechnology primarily deals with industrial-scale production of biopharmaceuticals and biologicals using genetically modified microbes, fungi, plants, and animals.
  • Key application areas include:
    • Therapeutics (Medicines)
    • Diagnostics
    • Genetically Modified Crops (GMCs) for agriculture
    • Processed food
    • Bioremediation
    • Waste treatment
    • Energy production
  • Three critical research areas of biotechnology:
    1. Providing the best catalyst (microbe or pure enzyme).
    2. Creating optimal conditions (engineering) for the catalyst to function.
    3. Downstream processing technologies to purify the protein/organic compound.

II. Biotechnological Applications in Agriculture

  • Need for GMOs: Conventional agriculture faces limitations in yield increase. Agrochemicals (fertilisers, pesticides) are expensive and have harmful environmental effects. Biotechnology offers solutions like pest-resistant crops, reduced reliance on chemicals, and enhanced nutritional value.

  • Options for Increasing Food Production:

    1. Agrochemical-based agriculture.
    2. Organic agriculture.
    3. Genetically engineered crop-based agriculture (GM Crops).

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

  • Advantages of GM Plants:

    • Increased tolerance 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 (prevents early exhaustion of soil fertility).
    • Enhanced nutritional value of food, e.g., Vitamin A-enriched rice (Golden Rice).
    • Creation of 'tailor-made' plants for alternative resources (starches, fuels, pharmaceuticals) in industries.

  • Specific Examples:

    • Bt Cotton (Pest Resistance):
      • Source: Bacterium Bacillus thuringiensis (Bt).
      • Mechanism: Bt produces proteins (Cry proteins) that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles), and dipterans (flies, mosquitoes).
      • Gene: The gene encoding this toxin is called the cry gene (e.g., cryIAc, cryIIAb control cotton bollworms; cryIAb controls corn borer).
      • How it works: Bt produces inactive protoxins. When an insect ingests this, the alkaline pH of its gut solubilizes the crystals and activates the toxin. The activated toxin binds to the surface of midgut epithelial cells, creates pores, causing cell swelling, lysis, and eventually death of the insect.
      • Advantage: Specific to target insects, reducing the need for insecticide sprays. The toxin gene is incorporated into the plant genome, so the plant itself produces the toxin.
    • Pest Resistance using RNA Interference (RNAi):
      • Target: Nematode Meloidogyne incognita infecting roots of tobacco plants, reducing yield.
      • Mechanism: RNAi is a natural cellular defense mechanism in all eukaryotes. It involves silencing a specific mRNA due to a complementary double-stranded RNA (dsRNA) molecule binding to it and preventing its translation (silencing).
      • Application: Nematode-specific genes were introduced into the host plant using Agrobacterium vectors. This introduction was engineered such that both sense and anti-sense RNA strands were produced in the host cells. These two strands, being complementary, formed dsRNA, initiating RNAi.
      • Result: When the nematode feeds on the transgenic plant roots, it ingests the dsRNA. The dsRNA silences the specific essential mRNA in the nematode, leading to its death. The transgenic plant is thus protected.
    • Golden Rice (Nutritional Enhancement):
      • A genetically modified variety of rice (Oryza sativa).
      • Engineered to biosynthesize beta-carotene (a precursor of Vitamin A) in the edible parts (endosperm).
      • Aims to combat Vitamin A deficiency, especially in developing countries where rice is a staple food.

III. Biotechnological Applications in Medicine

  • Recombinant DNA technology has significantly impacted healthcare. Approximately 30 recombinant therapeutics have been approved worldwide (12 marketed in India).
  • Genetically Engineered Insulin:
    • Problem: Insulin used previously was extracted from slaughtered cattle and pigs, causing allergies or other immune responses in some patients.
    • Structure: Human insulin consists of two short polypeptide chains (Chain A and Chain B) linked by disulfide bridges. In humans, it's synthesized as a pro-hormone (pro-insulin) containing an extra stretch called the C-peptide, which is removed during maturation.
    • Challenge in rDNA: Producing mature insulin in E. coli was difficult because prokaryotic cells lack the machinery to process pro-insulin.
    • Solution (Eli Lilly, 1983): Prepared two DNA sequences corresponding to chains A and B. Introduced them into separate plasmids of E. coli to produce the chains individually. Extracted the chains and combined them by creating disulfide bonds to form functional human insulin (humulin).
  • Gene Therapy:
    • Concept: A collection of methods allowing correction of a gene defect diagnosed in a child/embryo. Involves delivering a normal gene into an individual or embryo to take over the function of and compensate for the non-functional gene.
    • First Clinical Gene Therapy (1990): Given to a 4-year-old girl with Adenosine Deaminase (ADA) deficiency.
    • ADA Deficiency: This enzyme is crucial for immune system function. Its deficiency leads to Severe Combined Immunodeficiency (SCID).
    • Treatment Approaches:
      • Bone Marrow Transplantation: Requires a suitable donor.
      • Enzyme Replacement Therapy: Functional ADA is given by injection, but it's not a permanent cure.
      • Gene Therapy (Somatic): Lymphocytes are extracted from the patient's blood, 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. However, these cells are not immortal, so periodic infusions are needed.
      • Potential Permanent Cure: If the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages.
  • Molecular Diagnosis:
    • Need: Conventional diagnostic methods (serum, urine analysis) often detect diseases too late. Early detection is crucial for effective treatment.
    • rDNA Technology, PCR, ELISA: Techniques allowing early diagnosis.
    • PCR (Polymerase Chain Reaction): Can detect very low concentrations of bacteria or viruses by amplifying their nucleic acid. Useful for detecting HIV in suspected AIDS patients (detects viral RNA/DNA before symptoms or antibodies appear) and genetic mutations.
    • ELISA (Enzyme-Linked Immunosorbent Assay): Based on the antigen-antibody interaction principle. Detects the presence of antigens (pathogen proteins, glycoproteins) or antibodies synthesized against the pathogen. Used widely for HIV testing and other infections.
    • Recombinant DNA Technology (Probes): A single-stranded DNA or RNA segment tagged with a radioactive molecule (probe) is allowed to hybridize to its complementary DNA in a clone of cells. This is followed by autoradiography. The probe will not hybridize with a mutated gene because the complementarity is lost. Used to detect gene mutations (e.g., cancer, genetic disorders).

IV. Transgenic Animals

  • Definition: Animals that have had their DNA manipulated to possess and express an extra (foreign) gene.
  • Common Examples: Rats, rabbits, pigs, sheep, cows, fish. Over 95% are mice.
  • Reasons for Creating Transgenic Animals:
    1. Normal Physiology and Development: Study gene regulation, effects on normal body functions, development (e.g., studying complex factors like insulin-like growth factor).
    2. Study of Disease: Serve as models for human diseases (e.g., cancer, cystic fibrosis, rheumatoid arthritis, Alzheimer's) to understand disease progression and test treatments.
    3. Biological Products: Produce useful biological products encoded by introduced genes.
      • α-1-antitrypsin: Used to treat emphysema.
      • Products for Phenylketonuria (PKU), Cystic Fibrosis.
      • Rosie (1997): First transgenic cow, produced human protein-enriched milk (2.4 g/L) containing human alpha-lactalbumin, nutritionally more balanced for human babies.
    4. Vaccine Safety: Used to test the safety of vaccines before human trials (e.g., transgenic mice for polio vaccine safety).
    5. Chemical Safety Testing (Toxicity Testing): Transgenic animals with genes making them more sensitive to toxic substances are used. Results are obtained more quickly than with non-transgenic animals.

V. Ethical Issues

  • Manipulation of living organisms raises ethical questions. Human intervention can have unpredictable results.
  • Regulation: Governments establish organizations to regulate genetic modification. In India, it's the GEAC (Genetic Engineering Approval Committee). GEAC makes decisions regarding the validity of GM research and the safety of introducing GMOs for public services.
  • Public Concerns: GMOs in food - potential effects on health, environment (gene flow, impact on non-target organisms).
  • Biopiracy: The use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned and without compensatory payment.
    • Developing countries are rich in biodiversity and traditional knowledge related to bio-resources.
    • Developed countries often exploit this knowledge and these resources, patenting products derived from them without adequate compensation or recognition.
    • Example: Basmati rice (Indian variety patented by a US company), Turmeric, Neem.
  • Patents: Indian Parliament has recently cleared the second amendment of the Indian Patents Bill, addressing issues like patent terms, emergency provisions, research and development initiatives. This helps prevent unauthorized exploitation.

Multiple Choice Questions (MCQs)

  1. The specific cry genes incorporated into cotton plants to control cotton bollworms are:
    a) cryIAb and cryIIAc
    b) cryIAc and cryIIAb
    c) cryIAb and cryIAc
    d) cryIIAc and cryIIAb

  2. RNA interference (RNAi) is used to develop pest resistance in tobacco plants against which organism?
    a) Bacillus thuringiensis
    b) Meloidogyne incognita
    c) Cotton bollworm
    d) Agrobacterium tumefaciens

  3. The first clinical gene therapy was given in 1990 to a patient suffering from:
    a) Phenylketonuria (PKU)
    b) Cystic Fibrosis
    c) Adenosine Deaminase (ADA) deficiency
    d) Sickle Cell Anemia

  4. Which technique is based on the principle of antigen-antibody interaction for molecular diagnosis?
    a) PCR
    b) ELISA
    c) Autoradiography
    d) Gel Electrophoresis

  5. 'Rosie', the first transgenic cow, produced milk enriched with which human protein?
    a) Insulin
    b) Alpha-1-antitrypsin
    c) Beta-carotene
    d) Alpha-lactalbumin

  6. The inactive protoxin produced by Bacillus thuringiensis is converted into its active form in the insect gut due to:
    a) Acidic pH
    b) Alkaline pH
    c) Presence of specific enzymes
    d) High temperature

  7. Which organization in India makes decisions regarding the validity and safety of GM organisms?
    a) ICMR (Indian Council of Medical Research)
    b) CSIR (Council of Scientific and Industrial Research)
    c) GEAC (Genetic Engineering Approval Committee)
    d) DBT (Department of Biotechnology)

  8. Golden Rice is a genetically modified crop plant where the incorporated gene is meant for the biosynthesis of:
    a) Vitamin C
    b) Vitamin A (beta-carotene)
    c) Vitamin D
    d) Vitamin E

  9. The exploitation of bio-resources of a nation by organisations without authorization is termed:
    a) Bioremediation
    b) Bio-fortification
    c) Biopiracy
    d) Biotechnology

  10. In the production of genetically engineered insulin, the A and B polypeptide chains were produced separately in E. coli, extracted, and combined by creating:
    a) Peptide bonds
    b) Hydrogen bonds
    c) Disulfide bonds
    d) Glycosidic bonds

Answer Key:

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

Make sure you understand the concepts behind each point, especially the mechanisms like Bt toxin action and RNAi. The examples like Golden Rice, Bt Cotton, ADA therapy, and Rosie the cow are very important. Also, remember the ethical considerations and the role of GEAC. Good luck with your preparation!

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