Faulty outlooping produces λ phage containing bacterial DNA

The diagram shows how specialized transduction operates in phage λ. (a) A crossover at the specialized attachment site produces a lysogenic bacterium. (b) The lysogenic bacterium can produce a normal λ (i) or, rarely, λdgal (ii), a transducing particle containing the gal gene. (c) gal⁺ transductants can be produced by either (i) the co-incorporation of λdgal and λ (acting as a helper) or (ii) crossovers flanking the gal gene, a rare event. The blue double boxes are the bacterial attachment site, the purple double boxes are the λ attachment site, and the pairs of blue and purple boxes are hybrid integration sites, derived partly from E. coli and partly from λ.