Targeted transposition of a P{roX1-lacZ.R} element to the P{lArB} element in roX1MB710. The resulting chromosome contains a tandem insertion: it retains the P{lArB} insertion and also contains a P{roX1-lacZ.R} element (inserted adjacent to the 3' end of the P{lArB} insertion). The P{roX1-lacZ.R} element is oriented such that the 3' end of the element is proximal to the roX1 promoter.