Figure 3.

Genomic Southern analyses of ida7 probed with plasmid sequences and the IC140 gene. (A) Cosegregation of the ida7 motility defects and the NIT1 plasmid. Shown here are Southern blots of PstI-digested genomic DNA isolated from wild-type, the original ida7 strain, and the slow swimming progeny from two successive generations (F₁, F₂) of ida7 x nit1 crosses. The blot was hybridized to a probe containing vector sequence from the pMN24 (NIT1) plasmid. No vector bands are detectable in the wild-type sample, but three bands are visible in ida7 and in all of its slow swimming progeny. (B) Disruption of the IC140 gene by plasmid insertion. A Southern blot of NotI-digested genomic DNA from wild-type and ida7 was hybridized with an 11.5-kb XbaI genomic fragment containing the IC140 gene. One of the restriction fragments (indicated by the asterisk to the right) is shifted in the ida7 lane. (C) Shown here is a NotI restriction map of the genomic region surrounding the IC140 gene in wild-type (top), and a diagram of the pMN24 plasmid insertions in ida7 (bottom).