Figure 2.

PFGE of G418R clones derived from YAC yWXD1851 by circularization. After PFGE (Materials and Methods), DNA from nine independent transformants (lanes 1–9), from the parental YAC strain (lane 10), and from the AB1380 yeast strain containing no YAC (lane 11) were blotted onto a nylon membrane and hybridized with ³²P-labeled total human DNA to visualize YACs. The circular YACs that have the correct phenotype, requiring both tryptophan and uracil (lanes 1–4, 6 and 8) show only hybridization to labeled human DNA at the well and are inferred to be circular (see text); strains with other phenotypes (see text) show YACs at the position of a dimer (lanes 5 and 7) or the original YAC (lanes 9 and 10).