Sex and the Single (Double-Strand) Break Emmanuelle Martini, Scott Keeney  Molecular Cell  Volume 9, Issue 4, Pages 700-702 (April 2002) DOI: 10.1016/S1097-2765(02)00512-9

Figure 1 The Fate of a Double-Strand Break Is Influenced by the Presence or Absence of Breaks Elsewhere in the Genome A double-strand break made by the HO or VDE site-specific endonucleases can be repaired by any of several pathways (only a few homology-directed paths are shown). After DSB formation, the 5′ terminal strands on either side of the break are resected to yield 3′ single-stranded tails. If the DSB is flanked by direct repeats (red arrows) and if the resection tracts are long enough to include the repeats, intrachromosomal strand annealing can repair the break, and the intervening sequence plus one of the repeats are deleted (left pathway). Alternatively, if one of the 3′ single-stranded tails invades an intact homologous duplex (shown in blue), the break can be repaired to yield a crossover or noncrossover product (right pathway). In mitotically dividing cells, repair is biased to favor intrachromosomal (or intersister) events, and interchromosomal events that do occur usually yield a noncrossover configuration. In meiotic cells, interchromosomal events are favored and crossovers are frequently produced, similar to the situation for natural meiotic DSBs made by the Spo11 protein. Repair of an HO- or VDE-generated break during meiosis is strongly influenced by whether there are Spo11-induced DSBs elsewhere in the genome. The presence of other DSBs results in limits on the length of resection tracts, biased repair in favor of interchromosomal events, and promotion of crossing over. Molecular Cell 2002 9, 700-702DOI: (10.1016/S1097-2765(02)00512-9)