Fig. 4. Structure of sister chromatid recombination products. To derive the structures, genomic DNA from each LTGC clone was digested with the indicated restriction enzymes and subjected to Southern blot analysis. The total number of events obtained for each class is indicated. H, HindIII; N, NcoI; S, SalI; B, BamHI; Bst, BstXI; Sac, SacI; Spe, SpeI; X, XhoI, (X,H), either a XhoI or HindIII site.