Q80. Which biological source provides the cry genes widely used in insect-resistant crops?
[UPSC CDS — Practice]
- (a) Lactobacillus acidophilus
- (b) Rhizobium leguminosarum
- (c) Plasmodium vivax
- (d) Bacillus thuringiensis
Answer: (d) Bacillus thuringiensis
Explanation: Bacillus thuringiensis is a soil bacterium that produces a range of insecticidal Cry proteins. Scientists can transfer suitable cry genes into plants to obtain resistance to target insects. Different Cry proteins vary in their insect specificity.
Q79. The insecticidal activity of many Bt Cry proteins is associated with:
[UPSC NDA — Practice]
- (a) Blocking plant photosynthesis
- (b) Destroying all soil fungi
- (c) Damage to susceptible insect gut cells
- (d) Inducing chlorophyll loss in rice
Answer: (c) Damage to susceptible insect gut cells
Explanation: In susceptible insects, activated Cry proteins interact with midgut structures and disrupt epithelial cell integrity, causing lethal damage. Toxicity depends on the specific protein and insect. Resistance management is needed because pest populations may evolve reduced susceptibility.
Q78. Golden Rice gains its yellow-orange appearance mainly from accumulation of:
[State PSC — Practice]
- (a) Haemoglobin
- (b) Beta-carotene
- (c) Anthocyanin
- (d) Melanin
Answer: (b) Beta-carotene
Explanation: Golden Rice has been engineered to synthesise carotenoids in the normally pale endosperm. Beta-carotene gives the grain a golden appearance and can serve as a vitamin A precursor. Its nutrient content can vary with variety and storage conditions.
Q77. In the pair “CRISPR–Cas9 — particle physics”, what is wrong?
[UPSC CSE (Pre) 2018]
- (a) CRISPR–Cas9 is actually a genome-editing technology
- (b) No RNA is involved in CRISPR
- (c) CRISPR stands for an Indian satellite
- (d) Cas9 is an astronomical instrument
Answer: (a) CRISPR–Cas9 is actually a genome-editing technology
Explanation: CRISPR–Cas9 belongs to genetic engineering, not particle physics. A guide RNA directs the Cas9 protein to a complementary DNA target for cutting. Its discovery advanced biotechnology, plant improvement and biomedical research, although off-target modifications remain a concern.
Q76. Flavr Savr tomato was engineered primarily to alter which process?
[UPSC CSE — Practice]
- (a) Nitrogen fixation in roots
- (b) Synthesis of human insulin
- (c) Chlorophyll production in seeds
- (d) Fruit softening related to polygalacturonase
Answer: (d) Fruit softening related to polygalacturonase
Explanation: Flavr Savr used antisense technology to reduce expression of a polygalacturonase enzyme involved in cell-wall breakdown. It was designed to delay softening of tomatoes. The product became the first commercially marketed genetically engineered whole food in 1994.
Q75. What is antisense RNA designed to do in a gene-regulation experiment?
[WBCS — Practice]
- (a) Destroy every ribosome in the cell
- (b) Replicate independently as a chromosome
- (c) Bind a complementary RNA and interfere with its expression
- (d) Convert an amino acid to a nucleotide
Answer: (c) Bind a complementary RNA and interfere with its expression
Explanation: An antisense RNA is complementary to a chosen RNA sequence. Base pairing can interfere with translation, RNA processing or RNA stability. Antisense approaches demonstrated that gene expression could be suppressed without directly deleting the gene.
Q74. Which genetically modified crop was approved for commercial cultivation in India in 2002?
[MPPSC — Practice]
- (a) Flavr Savr tomato
- (b) Bt cotton
- (c) GM wheat
- (d) Golden Rice
Answer: (b) Bt cotton
Explanation: Bt cotton received commercial cultivation approval in India in 2002. It became a major example in discussions of agricultural biotechnology, resistance management and biosafety. Approval of one crop does not imply approval of all genetically engineered crops.
Q73. Choose correct statements about environmental bioremediation:
1. It enhances natural microbial degradation.
2. All heavy metals can be completely degraded biologically.
3. Engineered microbes may be used.
[UPSC CSE (Pre) 2017]
- (a) 1 and 3 only
- (b) 1, 2 and 3
- (c) 2 and 3 only
- (d) 1 only
Answer: (a) 1 and 3 only
Explanation: Microorganisms can metabolise many organic pollutants, and genetic engineering may improve these pathways. Heavy metals are elements; they cannot be biodegraded into non-elements. Microbes may instead transform, immobilise or accumulate metals. Therefore statements one and three are valid.
Q72. The purpose of an insect-resistance refuge strategy around Bt crops is primarily to:
[UPPCS — Practice]
- (a) Increase pesticide use automatically
- (b) Prevent root formation
- (c) Make crops sterile
- (d) Slow selection for Bt-resistant pest populations
Answer: (d) Slow selection for Bt-resistant pest populations
Explanation: Refuge areas maintain susceptible insects that can mate with individuals surviving Bt exposure. This can delay the spread of resistance genes under suitable biological conditions. Effective resistance management also depends on toxin expression and pest biology.
Q71. Which property is targeted by engineering salt-tolerant crop varieties?
[RAS / RPSC — Practice]
- (a) Production of red blood cells
- (b) Formation of animal antibodies
- (c) Tolerance of saline growing conditions
- (d) Absence of all stomata
Answer: (c) Tolerance of saline growing conditions
Explanation: Salinity-tolerance engineering explores ion transport, osmotic adjustment, stress signalling and protective metabolites. These pathways can help plants maintain growth when soils contain excess salts. A single genetic modification rarely solves every environmental limitation affecting yields.
