MCQ Bank

Plant cells contain many chloroplasts, and each chloroplast can contain multiple copies of the introduced transgene. This high gene copy number can result in substantially higher levels of transgene expression.

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Q21

When using Agrobacterium tumefaciens for plant transformation, the Ti-plasmid is modified to be "disarmed." What is the primary purpose of this disarming?

A) To make the plasmid easier to insert into the bacterium.
B) To increase the copy number of the plasmid in Agrobacterium
C) To prevent the transfer of tumor-forming genes to the plant genome.
D) To allow the plasmid to replicate in plant cells.

AI Explanation

Disarming the Ti-plasmid removes or inactivates the genes responsible for tumor formation while retaining the machinery needed for T-DNA transfer. This makes Agrobacterium a safer and useful genetic transformation tool.

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Q22

In its natural state, Agrobacterium transfers T-DNA that includes genes for phytohormone synthesis. What is the evolutionary advantage for the bacterium in having the plant produce these hormones?

A) To increase the plant's photosynthetic rate.
B) To create a nutrient-rich environment (opines) for the bacterium to consume.
C) To strengthen the plant cell walls.
D) To make the plant resistant to insects.

AI Explanation

Agrobacterium-induced plant cells produce opines as a consequence of T-DNA gene expression. These compounds serve as specialised nutrient sources that the bacterium can utilise, providing an evolutionary advantage.

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Q23

A scientist is reviewing gene transfer methods. They note that "Chemical and physical direct DNA transfer" is a distinct category from "Bacterial gene delivery." What fundamental conceptual difference best separates these categories?

A) The cost and time involved.
B) The ploidy level of the recipient plant cells.
C) The type of gene being transferred.
D) Whether a biological vector is used.

AI Explanation

Bacterial gene delivery uses a living biological vector such as Agrobacterium to transfer DNA into plant cells. Direct chemical or physical methods deliver DNA without relying on a biological vector.

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Q24

Compared to Agrobacterium-mediated transformation, particle bombardment is often preferred for transforming cereal crops like wheat and rice. What is the most relevant analytical reason for this preference?

A) Particle bombardment is a much older and more trusted technology.
B) Agrobacterium does not naturally infect monocots like cereals as efficiently as dicots.
C) Particle bombardment never causes genomic rearrangements.
D) Particle bombardment is always cheaper and faster.

AI Explanation

Agrobacterium naturally has a broader and historically more effective transformation capability in many dicot plants. Particle bombardment can therefore be useful for cereal crops such as wheat and rice, where transformation by Agrobacterium has traditionally been more challenging.