Q1. Which part of the plant is best suited for making virus-free plants and why?
Answer: The part of the plant best suited for making virus-free plants is the meristem. It is because the meristem remains virus-free even when the rest of the plant is infected.The viruses spread slowly and cannot reach the actively dividing cells in the meristem.
Hence, by culturing the meristem in vitro, healthy and virus-free plants can be regenerated.

Q2. What is the major advantage of producing plants by micropropagation?
Answer: The major advantage of producing plants by micropropagation (the method of producing thousands of plants through tissue culture) is the ability to achieve propagation of a large number of plants in very short durations. Additionally, all the plants produced will be genetically identical to the original plant.

Q3. Find out what the various components of the medium used for propagation of an explant in vitro are?
Answer: The nutrient medium used for propagation of an explant in vitro must provide:

1. A carbon source such as sucrose.
2. Inorganic salts.
3. Vitamins.
4. Amino acids.
5. Growth regulators like auxins and cytokinins.

Q4. Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because
(a) bacteria are resistant to the toxin
(b) toxin is immature;
(c) toxin is inactive;
(d) bacteria encloses toxin in a special sac.
Answer: (c) The toxin is inactive.

Q5. What are transgenic bacteria? Illustrate using any one example.
Answer: Transgenic bacteria are bacteria that have been genetically modified to carry and express a foreign gene from another organism.

Transgenic Bacteria are used to produce human insulin, scientists inserted DNA sequences coding for the A and B chains of insulin into plasmids of E. coli bacteria. These bacteria produced the two chains separately, which were later extracted and chemically joined to form functional human insulin. Hence, the genetically engineered E. coli are called transgenic bacteria, as they act as biological factories for producing human insulin used in the treatment of diabetes.

Q6. Compare and contrast the advantages and disadvantages of production of genetically modified crops.
Answer: Genetically Modified (GM) Crops are plants whose genes are altered to express desired traits such as pest resistance, higher yield, or improved nutrition.

Advantages of genetically modified crops are:

1. Higher Yield: GM crops produce more yield and reduce post-harvest losses.
2. Pest Resistance: Crops like Bt cotton are resistant to insect pests, reducing pesticide use.
3. Soil Fertility: GM crops use minerals more efficiently, preventing early soil exhaustion.
4. Improved Nutrition: Crops such as Golden Rice are enriched with Vitamin A.
5. Stress Tolerance: GM crops can tolerate drought, cold, salinity, and heat.
6. Resource Production: Used to produce starches, fuels, and medicines.

Disadvantages of genetically modified crops are:

1. Environmental Risks: May harm non-target insects or disrupt ecosystems.
2. Unpredictable Effects: Introduction into the environment can lead to unforeseen consequences.
3. Ethical Concerns: Genetic manipulation raises moral and social debates.
4. Patent Issues: Leads to problems of biopiracy and monopoly by biotech companies (e.g., Basmati rice case).

Q7. What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?
Answer: Cry proteins are insecticidal proteins encoded by cry genes that form crystalline inclusions during a specific growth phase of certain bacteria. These proteins exist as inactive protoxins and become active only in the alkaline gut of insect larvae, where they destroy the gut lining and kill the pests. Cry proteins are produced by the bacterium Bacillus thuringiensis (Bt).

Humans have isolated the Bt cry gene and introduced it into crop plants like Bt cotton and Bt corn. These transgenic plants produce the Cry protein themselves, making them naturally resistant to insect pests. This helps reduce the use of chemical pesticides and improves crop yield and sustainability.

Q8. What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
Answer: Gene therapy is a collection of methods that allows the correction of a gene defect that has been diagnosed in a child or embryo. In this therapy, genes are inserted into a person’s cells and tissues to treat a disease.

Adenosine deaminase (ADA) deficiency is a genetic disorder caused by the deletion or inactivation of the gene encoding the ADA enzyme, which is essential for the proper functioning of the immune system. Its absence leads to the accumulation of toxic metabolites that destroy lymphocytes, resulting in severe immunodeficiency.

Therapy Steps (First Clinical Gene Therapy, 1990):

1. Lymphocytes are isolated from the patient’s blood and cultured outside the body.
2. A functional ADA cDNA is inserted into these cells using a retroviral vector.
3. The genetically modified lymphocytes expressing the ADA enzyme are reintroduced into the patient’s bloodstream.

Since lymphocytes are short-lived, this treatment requires repeated infusions of modified cells. However, if the functional ADA gene is inserted into embryonic cells, it could offer a permanent and lifelong cure.

Q9. Diagrammatically represent the experimental steps in cloning and expressing a human gene (say the gene for growth hormone) into a bacterium like E. coli.
Answer: The key experimental steps involved are:

1. Identification and Isolation of DNA: Identify and isolate the human gene (for growth hormone) from the human cell.
2. Cutting DNA: Cut both the isolated human DNA and the plasmid vector DNA at specific sites using the same restriction enzyme (molecular scissors).
3. Ligation: Join the human gene fragment to the cut vector DNA using DNA ligase to create a recombinant DNA molecule.
4. Transformation: Transfer the recombinant DNA into the host bacterium (E. coli) after making it competent to take up DNA.
5. Selection and Cloning: Selectively grow the transformed host cells using selectable markers like antibiotic resistance genes. As bacteria replicate, the recombinant DNA also replicates.
6. Expression and Extraction: Optimise conditions to induce the expression of the foreign gene to produce the recombinant protein (human growth hormone), followed by downstream processing (separation and purification).

Q10. Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of rDNA technology and chemistry of oil?
Answer: Based on the understanding of rDNA technology and oil chemistry, one could target the metabolic pathway of oil synthesis.

1. Identify Target Gene: Identify the gene(s) in the seed that code for enzyme(s) crucial for oil synthesis or accumulation.
2. Gene Silencing (RNAi): Use RNA interference (RNAi) to silence the specific mRNA of the identified oil-producing gene.
3. Introduction of dsRNA: Construct a vector (rDNA molecule) that, when introduced into the plant using Agrobacterium, produces both sense and antisense RNA corresponding to the oil-synthesis gene.
4. Silencing: The sense and antisense RNAs form a complementary dsRNA that initiates RNAi, thereby silencing the specific mRNA. This stops or reduces the translation of the enzyme required for oil synthesis, effectively reducing oil content.

Q11. Find out from the internet what is golden rice.
Answer: Golden rice is an example of a genetically modified (GM) crop created to enhance the nutritional value of food. It is a variety of rice that has been Vitamin A enriched to combat Vitamin A deficiency in populations dependent on rice.

Q12. Does our blood have proteases and nucleases?
Answer: Yes, our blood has both proteases and nucleases.

• Proteases: The human body synthesises enzymes that break down proteins. For instance, some proteins involved in blood clotting are proteases, and the immune system uses proteases to process antigens and destroy pathogens.
• Nucleases: These enzymes (exonucleases and endonucleases) are present in blood cells and are used for DNA repair, replication, and breakdown of foreign nucleic acids from invading pathogens such as viruses and bacteria.

Q13. Consult the internet and find out how to make orally active protein pharmaceuticals. What is the major problem to be encountered?
Answer: To make orally active protein drugs, scientists use two main strategies known as encapsulation and chemical modification. In encapsulation, proteins are enclosed within micro or nanoparticles such as liposomes or polymeric capsules. These protective coatings shield the proteins from stomach acid and digestive enzymes, allowing them to reach the intestine for absorption. In chemical modification, proteins are pegylated or structurally engineered to enhance their stability, making them more resistant to degradation by enzymes in the digestive tract.

Major problems to be encountered are:

1. Degradation in the stomach: Strong acid and digestive enzymes (proteases) break down proteins into amino acids before they can act.
2. Poor absorption: Even stable proteins struggle to cross the intestinal wall because they are large and water-soluble molecules.