Practice question

Specialized transduction occurs only with temperate phages that integrate at specific attachment site forming prophage. Upon induction, excision normally precise, but rare imprecise excision deletes part of prophage and captures adjacent bacterial genes, such as lambda gal and bio near attB in E. coli. Resulting defective phage carries bacterial genes but lacks essential phage genes, requiring helper phage for propagation. Only genes flanking integration site transfer, at high frequency for those markers, not random genome. This specificity contrasts generalized transduction and explains lambda transducing phages lambda dgal and lambda dbio.