The inverted dimeric plasmid integration preserves both palindromic junctions, creating an inverted triplication of <i>ARS1</i>.

<p>(A) The map illustrates the expected structure after homologous integration of the dimeric plasmid between <i>TRP1</i> and <i>GAL3</i> on chromosome IV. The positions and sizes of <i>Bgl</i>II fragments, as well as probe sequences are illustrated. (B) A snap-back assay detects palindromic sequences by virtue of their ability to recreate duplex fragments of half the original size after boiling and quick cooling on ice. Additionally, these sequences are resistant to the ssDNA nuclease S1. (C and D) Southern blots of snap-back assays on the two palindromic junctions of the integrated plasmid in the last day clone from transformant #7. Lane 1 = native duplex <i>Bgl</i>II fragments; lane 2 = denatured/renatured palindromic duplexes; lane 3 = S1 nuclease resistant duplex DNA. The probe in (C) detects the <i>URA3</i> palindromic fragment; the probe in (D) detects the <i>ARS1</i> palindromic fragment as well as the non-inverted copy of <i>ARS1</i> adjacent to <i>GAL3</i>. Note that the larger ssDNA fragment (in lane 2) is degraded by S1 (lane 3).