Gene delivery by microinjection—method classification Microinjection of nucleic acids (NA) directly into plant or animal cells is best classified as which type of gene transfer method?
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APhysical method
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BBiological method
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CCombination of physical and biological method
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DChemical method
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EEnzymatic method only
Answer
Correct Answer: Physical method
Explanation
Introduction / Context:Microinjection introduces DNA or RNA directly into cells using fine glass needles or microneedle systems under microscopic control. This bypasses carrier organisms and relies on physical penetration of the plasma or nuclear membrane.
Given Data / Assumptions:
- Nucleic acids are delivered cell-by-cell.
- No vector (like Agrobacterium) is required.
- Specialized equipment (micromanipulators) is used.
Concept / Approach:Classify based on mechanism. Biological methods use living vectors (e.g., Agrobacterium, viruses). Chemical methods rely on PEG, calcium phosphate, or liposomes. Physical methods include microinjection, particle bombardment, electroporation, and laser poration.
Step-by-Step Solution:
Identify absence of biological vector → not biological.Identify direct, mechanical entry → a physical approach.Conclude microinjection is a physical gene transfer technique.Verification / Alternative check:Protocols categorize microinjection with other direct methods in gene transfer manuals.
Why Other Options Are Wrong:
- Biological methods use organisms; not applicable here.
- Chemical agents alone are not the mechanism.
- “Combination” is unnecessary; the defining trait is physical penetration.
Common Pitfalls:Assuming microinjection scales easily; it is labor-intensive and typically for large cells, oocytes, or early embryos.
Final Answer:Physical method