DNA delivery by microinjection — Which statement is NOT true about microinjecting DNA into plant protoplasts?
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AIt is performed with the aid of a micromanipulator and microcapillary setup
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BRecipient cells are immobilized on a support or gently held to a substrate for stability
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CIt employs a needle with a diameter greater than the cell diameter
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DAll of the above are true
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EIt typically uses a fine glass capillary needle smaller than the cell diameter
Answer
Correct Answer: It employs a needle with a diameter greater than the cell diameter
Explanation
Introduction / Context:Microinjection is a direct physical method for introducing DNA, RNA, or proteins into individual plant cells or protoplasts. The technique requires precision instrumentation and gentle handling to avoid lysis, especially because protoplasts lack a cell wall and are osmotically fragile.
Given Data / Assumptions:
- Protoplasts are spherical, wall-less cells enclosed only by a plasma membrane.
- Micromanipulators and microcapillaries are standard equipment.
- Cells must be stabilized during injection to prevent movement and damage.
Concept / Approach:The microinjection needle must be substantially finer than the target cell to penetrate the membrane with minimal disruption. A needle larger than the cell diameter would catastrophically damage the cell. Therefore, the statement claiming a larger-than-cell needle is used is not true.
Step-by-Step Solution:
Confirm core setup → micromanipulator and microcapillary are correct.Confirm immobilization → true for positional control.Evaluate needle size → must be smaller than the cell; a larger needle is incorrect → choose option (c) as NOT true.Verification / Alternative check:Protocols specify tip diameters in the submicron to a few microns range, far below typical protoplast diameters (20–50 microns).
Why Other Options Are Wrong:
a,b) Both accurately describe the procedure.d) Cannot be true because (c) is false.e) Reaffirms correct practice (fine needle smaller than cell diameter).Common Pitfalls:Using excessive injection pressure or a too-wide tip causes lysis; osmotic stabilization and gentle manipulation are essential.
Final Answer:It employs a needle with a diameter greater than the cell diameter.