Exercises

1. Which part of the plant is best suited for making virus-free plants and why?

• The meristem (both apical and axillary) is best suited for this purpose.
• Why: Even if a plant is infected with a virus, the meristematic tissue remains virus-free because the rate of cell division is faster than the rate of viral multiplication, and there is a lack of vascular connections in this region.

2. What is the major advantage of producing plants by micropropagation?

• The primary advantage is the ability to produce a large number of plants in a very short duration.
• The resulting plants (somaclones) are genetically identical to the original plant, ensuring the preservation of desirable traits.

3. Find out what the various components of the medium used for propagation of an explant in vitro are?

• Carbon source: Usually sucrose.
• Inorganic salts: Macro and micronutrients.
• Vitamins: e.g., Thiamine, Nicotinic acid.
• Amino acids.
• Growth regulators: Auxins (for rooting) and Cytokinins (for shoot induction).

4. Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because –

• (c) toxin is inactive.
• Explanation: The Bt toxin exists as an inactive protoxin in the bacteria. It only becomes active in the alkaline environment of an insect's gut.

5. What are transgenic bacteria? Illustrate using any one example.

• Transgenic bacteria are bacteria whose DNA has been manipulated to carry and express a foreign gene.
• Example: E. coli bacteria engineered with human DNA sequences to produce human insulin (Humulin).

6. Compare and contrast the advantages and disadvantages of production of genetically modified crops.

• Advantages:
  1. Tolerance to abiotic stresses (drought, salt).
  2. Reduced reliance on chemical pesticides.
  3. Enhanced nutritional value (e.g., Vitamin A in Golden Rice).
  4. Reduced post-harvest losses.
• Disadvantages:
  1. Potential for unpredictable effects on the ecosystem.
  2. Risk of horizontal gene transfer to weeds ('superweeds').
  3. Allergenic potential of new proteins.
  4. Ethical and economic concerns (patents, biopiracy).

7. What are Cry proteins? Name an organism that produce it. How has man exploited this protein?

• Cry proteins are toxic insecticidal crystals produced by the bacterium Bacillus thuringiensis.
• Exploitation: Scientists isolated specific cry genes and incorporated them into crop plants like Bt Cotton. These plants now produce the toxin themselves, making them resistant to specific insect pests like bollworms without the need for external insecticides.

8. What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.

• Gene therapy is a technique to correct a genetic defect by delivering a normal, functional gene into an individual's cells to replace a non-functional one.
• ADA Deficiency:
  1. Caused by the deletion of the gene for ADA, crucial for the immune system.
  2. Lymphocytes are extracted from the patient and grown in culture.
  3. A functional ADA cDNA is introduced into these cells using a retroviral vector.
  4. The modified cells are returned to the patient.
  5. Permanent cure is possible if the gene is introduced at the early embryonic stage.

9. Diagrammatically represent the experimental steps in cloning and expressing a human gene into E. coli. (Answer involves a flowchart showing: 1. Isolation of Human Gene & Plasmid → 2. Digestion with Restriction Enzyme → 3. Ligation → 4. Transformation into E. coli → 5. Selection of Transformants → 6. Expression in Bioreactor)

10. Can you suggest a method to remove oil (hydrocarbon) from seeds based on understanding of rDNA technology?

• By using antisense RNA technology or RNA interference (RNAi) to silence the specific enzymes (like glycerol-3-phosphate acyltransferase) responsible for the synthesis of oils/lipids in the seed during development.

11. Find out from internet what is golden rice.

• Golden Rice is a variety of Oryza sativa (rice) produced through genetic engineering to biosynthesize beta-carotene, a precursor of Vitamin A, in the edible parts of the rice. It was developed to combat Vitamin A deficiency in developing countries.

12. Does our blood have proteases and nucleases?

• Yes. Blood contains various proteases (e.g., thrombin involved in clotting) and small amounts of nucleases. However, they are regulated by inhibitors to prevent damage to the body's own proteins and cells.

13. How to make orally active protein pharmaceutical? What is the major problem?

• Method: Encapsulation in liposomes or protective polymers that can withstand stomach acid.
• Major Problem: Proteins are easily degraded by the proteases and low pH (acidic environment) in the human stomach/digestive tract before they can be absorbed into the bloodstream.