Specialized transduction involves transfer of bacterial genes by what type of phage?

• A. A lytic phage packaging random DNA
• B. A temperate phage transferring genes adjacent to the prophage
• C. A phage delivering toxins by generalized transduction
• D. Conjugative plasmid transfer mediated by pili

Answer: (B)

Specialized transduction happens only with temperate phages that integrate into the bacterial chromosome as prophages. When these prophages are induced to exit the chromosome, they can do so imprecisely and carry along genes that are right next to the prophage insertion site. The resulting phage particles then transfer those specific adjacent bacterial genes to a new host. This is different from generalized transduction, where a lytic phage accidentally packages random pieces of host DNA, and from conjugation, which moves DNA via pili without a phage involved. So transferring genes near the prophage by a temperate phage matches specialized transduction.