In enucleation of a mature, unfertilized ovum for cloning or experimental manipulations, which methods can be used to remove or inactivate the nuclear material?
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AIrradiation (e.g., ultraviolet) to inactivate the nucleus
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BMicrosurgical removal of the nucleus with microneedles
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CBoth irradiation and microsurgical removal can be used
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DNeutralization and homogenization of the whole oocyte
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EAntibody-mediated nuclear digestion in vivo
Answer
Correct Answer: Both irradiation and microsurgical removal can be used
Explanation
Introduction / Context:Removal or inactivation of the oocyte nucleus (enucleation) is a key step in somatic cell nuclear transfer and certain developmental biology experiments. The method chosen must eliminate maternal nuclear DNA while preserving cytoplasmic integrity for subsequent reprogramming.
Given Data / Assumptions:
- Target cell is a mature unfertilized ovum (metaphase II).
- Goal is to remove or inactivate the maternal nucleus (germinal vesicle or metaphase plate).
- Oocyte viability postprocedure is essential.
Concept / Approach:Two classic approaches are used: (1) microsurgical removal of the nucleus using fine glass needles under a microscope; (2) ultraviolet irradiation to inactivate nuclear DNA while preserving cytoplasm. Choice depends on species, equipment, and downstream application.
Step-by-Step Solution:
Identify acceptable enucleation methods that preserve oocyte cytoplasm.Acknowledge both UV inactivation and microsurgery are documented approaches.Select “both (a) and (b).”Verification / Alternative check:Published SCNT protocols across mammals (e.g., bovine, ovine) and amphibians (Xenopus) describe both strategies, confirming applicability.
Why Other Options Are Wrong:
- Neutralization/homogenization destroys cellular architecture.
- Antibody-mediated nuclear digestion is not a standard, practical enucleation method.
Common Pitfalls:Overexposure to UV damaging cytoplasm; mechanical trauma during microsurgery reducing developmental competence.
Final Answer:Both irradiation and microsurgical removal can be used