Mapping the vaa gene. The vaa gene was mapped on existing physical and genetic maps using pulsed field gel electrophoresis and Southern blotting . A: the location of the vaa gene on the physical maps of five M. hominis isolates PG21, 4195, 132, 93 and 7488. The vaa gene mapped to the same genomic region for all isolates (shown in red). B: Pulsed field gel electrophoresis and Southern blotting results used for mapping of vaa in M. hominis 7488. Digests of four out of five enzymes used is shown. The probes 1 to 3 are denoted P1 to 3. The sizes of the bands reacting with the probes are indicated on the left side of the figure.