Chromosome breakage in InvBE <i>recB</i> and InvA <i>recA recD</i> mutants.

<p>Chromosomes of the indicated InvBE mutants, grown in minimal medium (MM) or for 1, 2 or 3 hours in LB, were cleaved with the I-<i>Sce</i>I enzyme and fragments were separated by PFGE. A. Ethidium bromide stained gel with I-<i>Sce</i>I cut chromosomes from InvBE <i>recB</i> and InvBE <i>recB recJ</i> mutants. First lane <i>Saccharomyces cerevisiae</i> chromosome ladder, relevant sizes are indicated on the left. B. Southern blot of the gel shown in A using the origin-proximal probe in the 800 kb I-<i>Sce</i>I fragment, both the intact fragment and fragments of smaller sizes hybridize with the probe. C. Southern blot of a gel made with the InvBE <i>recB</i> I-<i>Sce</i>I cut chromosomes, using the origin-distal probe in the 800 kb I-SceI fragment, only the intact I-<i>Sce</i>I fragment hybridizes with the probe. D. Ethidium bromide stained gel with I-<i>Sce</i>I cut chromosomes from the InvBE <i>recA recD</i> mutant. E. Southern blot of the gel shown in D using the origin-proximal probe in the 800 kb I-<i>Sce</i>I fragment, both the intact fragment and fragments of smaller sizes hybridize with the probe. F. Schematic representation of the different DNA fragments. The triangles represent the three <i>rrn</i> operons as indicated, the black circle represent <i>oriC</i> and the little bars above the lines represent the position of the origin-proximal (left) and origin-distal (right) probes.