MCQ on Molecular Genetics - Part - 3

1. Marker-assisted selection (MAS) relies on:
A) Morphological traits
B) DNA markers linked to traits of interest
C) Protein sequencing
D) Phenotypic selection only
Answer: B
Rationale: MAS uses DNA markers tightly linked to genes/QTLs for precise selection.

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2. Which of the following is a co-dominant molecular marker?
A) RAPD
B) SSR (microsatellite)
C) AFLP
D) ISSR
Answer: B
Rationale: SSR markers show both alleles in heterozygotes, hence co-dominant.

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3. QTL mapping is primarily used to:
A) Identify mutations
B) Locate chromosomal regions controlling quantitative traits
C) Increase hybrid vigor
D) Study protein interactions
Answer: B
Rationale: QTL (Quantitative Trait Loci) mapping links molecular markers to polygenic traits.

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4. The first crop in which a transgenic variety was commercialized was:
A) Cotton
B) Tomato
C) Rice
D) Soybean
Answer: B
Rationale: The Flavr Savr tomato (1994, USA) was the first approved transgenic crop.

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5. The term “Golden Rice” refers to a transgenic rice enriched with:
A) Iron
B) Vitamin A (β-carotene)
C) Protein
D) Zinc
Answer: B
Rationale: Golden Rice was engineered to produce β-carotene to combat vitamin A deficiency.

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6. Which technique is used for large-scale analysis of gene expression?
A) PCR
B) DNA microarray
C) Gel electrophoresis
D) Southern blot
Answer: B
Rationale: Microarrays allow simultaneous monitoring of thousands of genes.

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7. Which method delivers foreign DNA directly into plant cells using high-velocity microprojectiles?
A) Agrobacterium-mediated transformation
B) Electroporation
C) Biolistic gun (gene gun)
D) PEG-mediated uptake
Answer: C
Rationale: Gene gun shoots DNA-coated particles into plant tissues.

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8. The most widely used bacterium in plant genetic engineering is:
A) Bacillus subtilis
B) Agrobacterium tumefaciens
C) Rhizobium leguminosarum
D) Pseudomonas fluorescens
Answer: B
Rationale: A. tumefaciens carries the Ti plasmid used for DNA transfer to plants.

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9. In molecular breeding, “pyramiding” refers to:
A) Stacking multiple genes/QTLs into a single genotype
B) Using only one major gene for resistance
C) Building genetic maps
D) Gene silencing for trait suppression
Answer: A
Rationale: Gene pyramiding combines multiple resistance genes for durable protection.

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10. Genomic selection (GS) differs from MAS in that it:
A) Uses only morphological markers
B) Uses genome-wide marker information for prediction
C) Requires fewer markers than MAS
D) Is not used in plants
Answer: B
Rationale: GS uses statistical models with genome-wide SNPs to predict breeding values, unlike MAS that uses few trait-linked markers.