Assertion (A): The use of agrochemicals alone was insufficient to feed the growing human population despite the success of the Green Revolution. Reason (R): Agro-chemicals are often too expensive for farmers in the developing world, and existing crop varieties could not yield further increases using only conventional breeding.
The Green Revolution tripled the food supply but failed to keep pace with demand. Further yield increases were constrained because agrochemicals were costly for developing world farmers, and conventional breeding methods had reached their yield limits, necessitating new approaches like GM crops.
Question 452 of 494
📘 CLASS XII
Assertion (A): Whole plants can be regenerated from an explant, demonstrating the phenomenon of totipotency. Reason (R): Totipotency is the capacity of any plant cell or explant to generate a complete, whole new plant when grown under sterile conditions in specialized nutrient media.
Totipotency is the fundamental biological basis used in tissue culture and micro-propagation. It refers to the inherent capacity of any part of a plant (explant) to develop into a whole, mature plant under controlled, sterile in vitro conditions.
Question 453 of 494
📘 CLASS XII
Assertion (A): The successful production of genetically engineered human insulin required combining chains A and B *in vitro* after separate expression in E. coli. Reason (R): Producing insulin as a single pro-hormone in bacteria was challenging because *E. coli* lacks the necessary enzymatic machinery to remove the C peptide to form mature insulin.
The primary challenge was correctly assembling the A and B chains and removing the C peptide. Eli Lilly overcame this by producing the chains separately in *E. coli*, extracting them, and then combining them externally by introducing disulphide bonds.
Question 454 of 494
📘 CLASS XII
Assertion (A): The first clinical gene therapy was provided to a four-year-old girl suffering from Adenosine Deaminase (ADA) deficiency in 1990. Reason (R): ADA deficiency is a critical disorder because the enzyme ADA is essential for the proper functioning of the immune system.
The first clinical gene therapy targeted ADA deficiency in 1990. This condition severely compromises the immune system because the enzyme ADA is crucial for immune cell function; its deletion causes the disorder.
Question 455 of 494
📘 CLASS XII
Assertion (A): One of the primary uses of transgenic animals is to study normal physiology and development. Reason (R): By introducing foreign genes that alter factors like insulin-like growth factor, scientists can study the biological effects and roles of these factors in the body.
Transgenic animals are specifically designed to investigate gene regulation and how genes affect normal body functions and development. For instance, manipulating the insulin-like growth factor gene allows researchers to determine its biological role.
Question 456 of 494
📘 CLASS XII
Assertion (A): The use of conventional methods like serum and urine analysis is sufficient for the early detection of pathogenic diseases. Reason (R): Molecular diagnostic techniques like PCR and ELISA are generally used for diagnosis only when the concentration of the pathogen is very high and symptoms have already manifested.
A is False: Conventional methods fail at early detection. R is False: PCR and ELISA are superior precisely because they can detect pathogens at *very low* concentrations, *before* symptoms appear.
Question 457 of 494
📘 CLASS XII
Assertion (A): Transgenic plants are developed to reduce post-harvest losses. Reason (R): Genetic modification enables crops to be more tolerant to abiotic stresses like cold, drought, salt, and heat.
A is True: Reduced post-harvest loss is a benefit of GM plants. R is True: Increased tolerance to abiotic stresses is also a benefit of GM plants. However, R describes tolerance during growth (field conditions), which is not the primary cause for reduced post-harvest spoilage (A).
Question 458 of 494
📘 CLASS XII
Assertion (A): The use of Agrobacterium vectors is essential in creating nematode-resistant tobacco plants using RNAi. Reason (R): Agrobacterium vectors are used to introduce nematode-specific DNA into the host plant, ensuring that both sense and anti-sense RNA are produced, which forms dsRNA.
To initiate RNAi against the nematode *Meloidegyne incognitia*, the plant needs dsRNA complementary to the nematode mRNA. This is achieved by introducing DNA using *Agrobacterium* vectors, forcing the plant cells to produce both complementary sense and anti-sense RNAs.
Question 459 of 494
📘 CLASS XII
Assertion (A): Basmati rice was crossed with semi-dwarf varieties and patented by a US company in 1997. Reason (R): The patent was controversial because it was granted on a variety essentially derived from traditional Indian farmer varieties, raising issues of biopiracy.
The US company patented a "new" Basmati variety created by hybridizing traditional Indian varieties. This action is a classic example of biopiracy, where traditional knowledge and resources of a country (India) were exploited without authorization or compensatory payment.
Question 460 of 494
📘 CLASS XII
Assertion (A): Transgenic animals are routinely used to produce biological products such as human alpha-1-antitrypsin. Reason (R): This protein is used for the treatment of emphysema, demonstrating the capacity of transgenic animals to serve as 'biological factories' for expensive human therapeutics.
Transgenic animals can be created by inserting DNA sequences that code for specific human proteins. Alpha-1-antitrypsin is one such protein produced by transgenic animals for commercial use in treating human diseases like emphysema.
