Step 1: Understanding the Concept:
Bacteria can gain new DNA in a few classic ways, transformation, conjugation and transduction, and the question is asking specifically about the route that needs a virus as a carrier.
Step 2: Key Concept or Approach:
Focus on the phrase "virus mediated" in the question. Only one of the given terms actually involves a virus at all; the rest describe unrelated genetic events.
Step 3: Detailed Explanation:
Transformation happens when a bacterium picks up free DNA fragments straight from its surroundings, with no virus involved.
Transcription is the copying of DNA into RNA inside a single cell, so it never transfers DNA between cells.
Integration describes DNA settling into a host chromosome after it has already arrived, not the transfer step itself.
Transduction is the one process where a bacteriophage picks up a fragment of the first host's DNA by mistake while replicating and then delivers it into a second host cell during a later infection.
Step 4: Final Answer:
The virus-mediated transfer of host DNA between cells is called transduction.