Assertion (A): The nutrient medium required for growing an explant in vitro must provide only a carbon source and inorganic salts. Reason (R): Growth regulators such as auxins and cytokinins, as well as vitamins and amino acids, must also be supplied for the successful regeneration of a whole plant.
A is False: The medium requires a carbon source (like sucrose), inorganic salts, vitamins, amino acids, and growth regulators. R is True: Auxins and cytokinins are essential growth regulators necessary for the process of totipotency, enabling the explant to regenerate into a whole plant.
Question 432 of 494
📘 CLASS XII
Assertion (A): Molecular diagnosis using a probe relies on the principle that the probe hybridizes perfectly to the complementary target nucleic acid sequence. Reason (R): If a patient's cells contain a mutated gene, the probe will not exhibit complementarity, ensuring that the affected cells are not detected by autoradiography.
A probe is a single-stranded, radioactively tagged molecule that is designed to detect a normal sequence via hybridization. The lack of hybridization due to a mutation prevents the retention of the radioactive tag, causing the corresponding cloned cells not to appear on the photographic film, confirming the presence of the mutation.
Question 433 of 494
📘 CLASS XII
Assertion (A): Recombinant therapeutic drugs, such as human insulin, are considered safer than similar products isolated from non-human sources. Reason (R): Recombinant products are structurally identical to natural human proteins and thus do not induce unwanted immunological responses or carry the risk of infection.
Insulin extracted from animals (cattle/pigs) previously caused allergies or reactions due to the foreign protein. Recombinant therapeutics overcome this as they are structurally identical to the human version, making them safe and effective without the risk of immune responses or infection.
Question 434 of 494
📘 CLASS XII
Assertion (A): Gene therapy for ADA deficiency involving the infusion of genetically engineered lymphocytes must be performed periodically. Reason (R): The functional ADA cDNA is introduced into mature lymphocytes, which are not immortal and eventually die, requiring repeated treatment.
The first clinical gene therapy involved introducing the ADA gene into cultured lymphocytes. Since lymphocytes are not immortal, they have a limited lifespan, necessitating periodic infusion of the engineered cells to maintain immune function.
Question 435 of 494
📘 CLASS XII
Assertion (A): The developing and underdeveloped world is characterized by high biodiversity and a wealth of traditional knowledge related to bio-resources. Reason (R): This traditional knowledge is valuable as it can significantly reduce the time, effort, and expenditure required during the commercial development of modern products.
The developing and underdeveloped nations are rich in both biodiversity and associated traditional knowledge, unlike financially rich industrialized nations. R correctly identifies the key motivation for biopiracy: using this pre-existing traditional knowledge helps multinational companies bypass expensive and time-consuming research and development efforts.
Question 436 of 494
📘 CLASS XII
Assertion (A): Transgenic mice are being utilized to test the safety of vaccines, such as the polio vaccine. Reason (R): If transgenic mice are found to be reliable for vaccine testing, they could potentially replace the use of monkeys, reducing ethical concerns and costs.
Transgenic mice are actively being developed for vaccine safety testing, specifically mentioned in the context of the polio vaccine. A major goal of this development is to establish a reliable replacement model that would reduce reliance on non-human primates (monkeys) for mandatory safety testing.
Question 437 of 494
📘 CLASS XII
Assertion (A): In humans, insulin is initially synthesized as a pro-hormone that contains an extra peptide sequence. Reason (R): This extra stretch, the C peptide, is crucial for linking the A and B chains in the pro-hormone and ensuring proper folding, but it must be enzymatically removed to form the mature, functional hormone.
Insulin in mammals is synthesized as pro-insulin, similar to how pro-enzymes require processing. The C peptide connects chains A and B in the inactive pro-hormone. Its removal during maturation is necessary for the molecule to achieve its fully mature and functional state.
Question 438 of 494
📘 CLASS XII
Assertion (A): The applications of biotechnology are restricted to human health care and agriculture. Reason (R): Biotechnology is a diverse field that includes applications in diagnostics, bioremediation, waste treatment, processed food production, and energy production.
A is False: While therapeutics and agriculture are major areas, biotechnology applications are far broader. R is True: Biotechnology encompasses industrial scale production using GMOs across numerous sectors, including diagnostics, bioremediation, waste treatment, and energy.
Question 439 of 494
📘 CLASS XII
Assertion (A): Bt toxin crystals do not harm the producing bacterium, Bacillus thuringiensis, itself. Reason (R): The alkaline pH of the bacteria's cytoplasm keeps the protoxin inactive, but the ingestion by the insect provides the acidic pH required for activation.
A is True: The Bt toxin exists as an inactive protoxin within the bacteria. R is False: The toxin is activated due to the *alkaline* pH of the insect gut, which solubilizes the crystals, not an acidic pH.
Question 440 of 494
📘 CLASS XII
Assertion (A): Polymerase Chain Reaction (PCR) is highly effective for the early detection of diseases caused by viruses and bacteria. Reason (R): PCR can amplify even a very low concentration of nucleic acid from a pathogen, allowing detection before the organism load is high enough to produce visible symptoms.
Conventional methods often fail at early detection. PCR is critical because its amplification capability allows scientists to detect the pathogen's nucleic acid when its concentration is too low to cause symptoms, making diagnosis faster and treatment more effective.
