FIG. 24.

Lethality caused by double-strand breaks in the replicated portion of the genome in rorA mutants. The chromosome is depicted as a theta-replicating structure, with the single line representing duplex DNA. The origin of DNA replication is denoted by small open circles at the top of the chromosome; the terminus is shown as a solid circle at the bottom. If both daughter branches of a replicating chromosome are broken at positions close to each other, the double-strand breaks have more chances of being repaired in the WT cells than in rorA mutant cells, due to the increased DNA degradation in the latter.