Final answer:
Before attacking the target DNA, the transposase enzyme trims the 3'OH ends of the DNA to create a staggered cut. It then mediates the insertion of the transposon at a new DNA site and completes transposition by replicating the missing bases.
Step-by-step explanation:
Before attacking the region of the target DNA, the transposase enzyme performs a series of steps. After transcription of the transposase gene, the enzyme nicks the DNA and trims the 3'OH ends to create a staggered cut to excise the transposon. The transposase brings the transposon ends together during the cut step and mediates its insertion at a new DNA site. After ligation of the 3'OH ends of the transposon to the 5'OH at the insertion site, replication replaces the missing bases, generating the direct repeats of host cell genomic DNA at the insertion site. A final ligation step completes transposition.