Creating transgenic animals: routes of DNA delivery Which of the following are recognized methods of transfection or genetic material transfer used when making transgenic animals?
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ATransfer of whole nuclei (e.g., somatic cell nuclear transfer)
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BTransfer of whole chromosomes or defined chromosome fragments
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CDirect transfer of DNA (e.g., pronuclear microinjection, viral vectors)
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DAll of the above
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ENone of the above; only selective breeding is used
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Transgenic animal production employs several routes to introduce genetic material. Understanding these options helps in selecting appropriate technology for trait insertion, gene knock-in, or complex genome edits.
Given Data / Assumptions:
- We consider laboratory-validated methods, not just theoretical possibilities.
- Goal is heritable modification of the germ line or creation of cloned transgenic animals.
Concept / Approach:Common routes include (1) nuclear transfer (moving an entire diploid nucleus into an enucleated oocyte), (2) chromosome transfer (microcell-mediated chromosome transfer), and (3) DNA delivery methods (pronuclear microinjection, lentiviral/retroviral vectors, transposons, CRISPR/Cas9 components).
Step-by-Step Solution:
Evaluate nucleus transfer: enables cloning and transgenesis from modified donor cells.Evaluate chromosome transfer: allows movement of large genetic payloads with native regulation.Evaluate DNA transfer: the most widely used approach for classic transgenics and gene editing.Conclude that all listed approaches are valid.Verification / Alternative check:Published protocols document successful animals generated via pronuclear microinjection, SCNT, viral transduction of embryos, and chromosome transfer.
Why Other Options Are Wrong:
- Each single-method option is incomplete.
- “None; only selective breeding” ignores modern genetic engineering.
Common Pitfalls:Assuming one method suits all species or edits; payload size, mosaicism risk, and regulatory context dictate method choice.
Final Answer:All of the above