SV40-based delivery: Recombinant SV40 viruses introduce foreign DNA into mammalian cells in what way?

Introduction / Context:
Simian Virus 40 (SV40) is a DNA tumor virus historically used as a cloning and expression vector in mammalian systems. Recombinant SV40 particles enter cells using viral entry mechanisms, bypassing classical chemical or physical transfection procedures.

Given Data / Assumptions:

• Recombinant SV40 vectors are packaged into infectious virions.
• Viruses naturally deliver their genomes to host cells.
• “DNA-mediated transfection” refers to methods like calcium phosphate, lipofection, or electroporation.

Concept / Approach:
Infection by an SV40 virion introduces the recombinant DNA directly through receptor-mediated entry, uncoating, and nuclear import of the viral genome. Therefore, one does not require separate DNA transfection protocols to achieve delivery—viral infection accomplishes it.

Step-by-Step Solution:

Verification / Alternative check:
Standard SV40 vector protocols rely on generating high-titer stocks and infecting cells, confirming that infection is the delivery route.

Why Other Options Are Wrong:

• With DNA-mediated transfection: unnecessary when using infectious virus.
• RNA-mediated transfection: irrelevant for a DNA virus system.
• Lipid fusion only or microinjection: not the typical SV40 delivery route.

Common Pitfalls:
Confusing transfection (non-viral) with transduction (viral delivery).

Final Answer:
Without DNA-mediated transfection (via viral infection)