Fig. 3. Complementation of dim-2 mutation. (A) Physical map of cosmid X25:A8 and related DNA segments. The positions of the dim-2 ORF (open box) and of restriction sites for NotI (N), EagI (E), Bsp120 I (Bs), EcoRI (R), HindIII (H) and MluI (M) are shown. (B) Southern analysis of methylation in the ζ-η region. The positions of EcoRI (R) and BamHI (B) restriction sites in the region are shown, and the size (kb) and origin of fragments that can be detected with the indicated probe are represented below the map. Sites that are sometimes methylated, and thus not digested, are marked with asterisks. EcoRI/BamHI digests of DNA from the following strains were probed to assess methylation at the ζ-η BamHI sites: a, wild-type (N150); b, dim-2¹ (N1257); c–e, N1257 transformed with pEK15, pEK14 and pEK19, respectively.