You amplify and sequence the integrated construct and flanking regions in both directions. on one side, your construct is flanked by a 5000-bp region of largely random sequence. on the other side, your construct is flanked by 200 "ttaggg" repeats. based on these results, propose a hypothesis as to why your construct is not expressed. you decide to reinject the same construct into another mouse embryo in an attempt to integrate the construct elsewhere in the genome. you are happy to find that this mouse does show gfp expression in every cell.