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GATE 2023 BT Q.44: solution and answer

GATE 2023 · BTQ.44 · 2 marks · MSQ

Direct DNA transfer method(s) used for plant genetic engineering is(are)

  1. (A)

    microparticle bombardment

  2. (B)

    electroporation

  3. (C)

    polyethylene glycol treatment

  4. (D)

    Agrobacterium-mediated transformation

See the question in the paper
GATE 2023 BT question 44Tap to open full size

Answer and solution

ANSWER

The direct DNA transfer methods used for plant genetic engineering are microparticle bombardment, electroporation, and polyethylene glycol (PEG) treatment — options A, B, and C.

Official answer: A, B, CSource: Official answer key, GATE 2023 BT (IIT Kanpur)

  1. Criterion: classify each option as a 'direct' (physical/chemical, vector-free) DNA delivery method versus a 'vector-mediated' (biological, indirect) method.

  2. (A) Microparticle bombardment (biolistics/gene gun): DNA-coated metal particles are physically accelerated into cells — no biological vector is involved. Direct method. Correct option.

  3. (B) Electroporation: an electric pulse transiently permeabilizes the plasma membrane (usually of protoplasts), letting naked DNA enter directly — no biological vector. Direct method. Correct option.

  4. (C) Polyethylene glycol (PEG) treatment: PEG destabilizes the protoplast plasma membrane, enabling direct chemical-mediated uptake of naked DNA — no biological vector. Direct method. Correct option.

  5. (D) Agrobacterium-mediated transformation: uses the bacterium's own Ti-plasmid T-DNA transfer machinery as a biological vector to deliver DNA into the plant genome — an indirect (vector-mediated), not direct, method. Incorrect option.

  6. Therefore the direct DNA transfer methods used for plant genetic engineering are (A), (B), and (C) only.

KEY IDEA

Direct (physical/chemical, vector-independent) DNA delivery methods for plants include microparticle bombardment (biolistics/gene gun), electroporation, and PEG-mediated uptake (typically into protoplasts); Agrobacterium-mediated transformation is an indirect, biological-vector method relying on the natural Ti-plasmid T-DNA transfer machinery.

WATCH OUT FOR

Students sometimes misclassify Agrobacterium-mediated transformation as a "direct" method because it is the most common and efficient transformation technique taught, forgetting that "direct" specifically means vector-independent (no biological carrier); Agrobacterium's Ti-plasmid T-DNA system makes it a vector-mediated (indirect) method regardless of its ubiquity.

From the GATE 2023 BT paper. Every question of this paper · Download the full paper · All 10 Enzymes & vectors questions, with notes

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