Figure 1.
Construction of the linear DNA substrate containing two pairs of inverted repeats. pID-IP*, derived from pID-IP by inactivation one of its NdeI sites, was used to generate pID-IP**, by inactivation of a BglII site located on the same side of the inverted dimer as the inactivated NdeI site (see Materials and Methods for details). The linear DNA-1 substrate containing two pairs of inverted repeats is the larger of the two fragments generated by BglII and NdeI digestion of pID-IP**. The length of the repeated H fragment in the HPH cassette is 350 bp and the length of the P fragment is 651 bp. The linear DNA-2 substrate without HPH/tet cassettes (only ΔPH sequences) was generated by digesting linear DNA-1 with EcoRV.