MCQ Bank

The first successful expression of foreign genes in plants was achieved in the early 1980s using recombinant DNA and plant transformation techniques. This established the foundation for modern plant genetic engineering.

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Q16

What is essential in the nutrient medium to maintain plant cells in an undifferentiated state for callus formation?

A) Correct balance of auxins, cytokinins, and gibberellins
B) High sugar concentration
C) Only auxins
D) Only cytokinins

AI Explanation

Plant cell differentiation and growth are controlled by the balance of plant hormones in the culture medium. Appropriate levels of auxins, cytokinins, and other growth regulators help maintain cells in an undifferentiated callus state.

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Q17

How is a cell suspension culture obtained?

A) By transferring callus into liquid medium with agitation
B) By grinding plant leaves
C) By freezing plant cells
D) By exposing cells to UV light

AI Explanation

Cell suspension cultures are commonly initiated by transferring friable callus into a liquid nutrient medium. Continuous agitation helps separate cells and small cell aggregates and keeps them suspended.

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Q18

A company wants to produce a very high yield of a recombinant vaccine protein in tobacco leaves. They are deciding between nuclear and chloroplast transformation. Which factor, specific to chloroplast transformation, provides the strongest argument for its use in this scenario?

A) Chloroplast genes are not subject to gene silencing.
B) Chloroplast transformation avoids the use of antibiotic resistance marker genes.
C) Chloroplasts are larger and easier to isolate.
D) The high copy number of chloroplasts per cell can lead to vastly higher protein accumulation.

AI Explanation

Chloroplast transformation can produce very high levels of recombinant protein because each cell contains many chloroplasts, and each chloroplast can contain multiple copies of the introduced DNA. This high gene dosage can substantially increase protein accumulation.

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Q19

A researcher in 1995 wanted to transform a novel ornamental plant species that had never been genetically modified before. Based on the historical development of plant transformation, what was the most significant challenge they likely faced?

A) Obtaining permission for field trials
B) Isolating the plant's DNA
C) Developing a routine transformation protocol for that specific species
D) Sequencing the plant's genome

AI Explanation

By 1995, plant transformation methods were established, but their efficiency varied considerably among plant species and genotypes. For a novel ornamental species, developing a reliable species-specific transformation and regeneration protocol would therefore have been a major challenge.

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Q20

Why is chloroplast transformation preferred for high-level transgene expression?

A) Chloroplast DNA is more stable than nuclear DNA
B) Thousands of chloroplasts per cell allow higher expression
C) Chloroplasts are not affected by RNA interference
D) Chloroplasts are easier to isolate

AI Explanation

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.

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Under normal conditions, transcription terminates:

A) At the ends of genes
B) At the beginning of the gene
C) In the middle of the gene
D) Only when DNA is damaged