Cell fusion in nuclear transfer — fusion of a karyoplast with an enucleated cell is commonly achieved in the presence of which agent?

Introduction / Context:
Somatic cell nuclear transfer and related micromanipulations may require fusing a donor nucleus (karyoplast) with an enucleated oocyte or recipient cell. Chemical or viral fusogens promote membrane merger for cytoplasmic-nuclear continuity.

Given Data / Assumptions:

• Karyoplast = nucleus with a thin rim of cytoplasm.
• Enucleated cell = cytoplast.
• Common fusogens include polyethylene glycol (PEG) and inactivated Sendai virus (HVJ).

Concept / Approach:

PEG dehydrates cell surfaces and promotes membrane fusion upon rehydration. Cytochalasin B disrupts actin polymerization and is used to assist enucleation or prevent cytokinesis, not primarily as a fusogen. Alcohol and RNase A are irrelevant to membrane fusion in this context.

Step-by-Step Solution:

Verification / Alternative check:

Protocol literature in cloning and hybrid cell production routinely employs PEG-mediated fusion or HVJ; cytochalasin is adjunct for enucleation but not the fusogen of choice.

Why Other Options Are Wrong:

(a) Not a fusogen; used to assist enucleation or block cytokinesis. (c) Incorrect because (a) is not a fusogen. (d) Alcohol does not mediate specific membrane fusion in this technique. (e) RNase A is unrelated.

Common Pitfalls:

Conflating enucleation aids (cytochalasin B) with fusogens; overlooking HVJ as an alternative to PEG.

Final Answer:

Polyethylene glycol (PEG)