Figure 1.

NMBAs of EcoRI-digested phage λ48.26 and its plasmid subclones. In each panel, the left lane is unassayed probe and the second and third lanes are the results of NMBAs in the presence of 100 and 300 μg/ml of cold competitor DNA, respectively. The three EcoRI bands marked with arrowheads are the insert fragments binding more strongly than both of the phage vector arms (λ1 and λ2) or the plasmid vector (P). Densitometry was used to confirm that the adjusted relative ratio of insert to vector DNA was high, as calculated previously (17). The relative ratios for the 300 μg/ml lanes are 40.9 (L48.26III), 15.1 (L48.26II), and 39.0 (L48.26I). The region analyzed at SNURF-SNRPN therefore contains a large MAR (gray bar).