Fig. 1. Southern blots of genomic DNA establish homologous gene replacement with Com6 site included. (A) Structure of the transforming DNA used. (B) Arrangement of restriction sites around the nsfA gene in Ax2 and in a homologous recombinant (HR) containing the Com6 site (marked by A). Restriction sites: P (PstI); H (HindIII); A (AflII); E (EcoRI); B (BamHI). The probe covers bases 1700-2860. (C) Blot of Ax2, ts1, ts2 and C6 (a pC6-derived clone) cut with B+H. (D) As in C, but cut with P and E±A. The main band at 2120 in Ax2 is insensitive to A; the HR lines are sensitive, showing that they each contain Com6. Additional bands are partial cleavages.