FIG. 4.

Southern blot of pooled integrated MLV vector products. Genomic DNA was collected from pooled MLV provirus-containing colonies for each of the vectors or vector pairs indicated at the top of the autoradiogram. This DNA was digested with ClaI and MluI, which produced a 5.6-kb band for all vectors as well as a shorter band diagnostic of either the intact (478 bp from Lac) or the corresponding deleted (316 bp from L∧c) ClaI-to-MluI region of lacZ. Lengths of predicted products are indicated at the left. The products in lane 3 are from transduction-type vectors used in the experiments described in Fig. 5.