Figure 7.—

Genetic testing of TID amplification structure. To determine whether an aTID junction is in orientation CD′ or DC′, a resistance determinant (tetRA) was added to the sequenced junction of strain TT25771 (see Table 1). The chromosome of the resulting strain is expected to be as diagrammed for strain 1 or strain 2 (circled). In a second transformation cross, a donor Cam^R determinant is introduced with one flanking sequence matching a reference region at the left and the other matching the tetRA sequence. The Cam^R determinant can be inherited only if the orientation of the recipient junction (tetRA or ARtet) matches that of the donor recombining sequence (right side of Cam^R). The donor fragments are designed such that inheritance of Cam^R creates a deletion of the region between the reference sequence and the right side of the Tet^R determinant in the recipient. The recipient strain is recA+ and was grown nonselectively before transformation.