DNA strand-exchange patterns associated with double-strand break-induced and spontaneous mitotic crossovers in Saccharomyces cerevisiae
Fig 6
Mechanisms that produce hetDNA on only one side of an initiating DSB.
Red and black lines represent recipient and donor sequences, respectively. Yellow boxes correspond to hetDNA and blue-filled triangles to sites of nicking by structure-selective endonucleases. The position of the initiating DSB is indicated by vertical gray lines. (A) Migration of an HJ back to the DSB site prior to second-end extension removes the hetDNA created by the initial strand invasion. (B) Migration of one of the HJs past the site of the DSB after second-end extension places both asymmetric hetDNA tracts on the same side of the break. The transition between the hetDNA tracts remains, but is displaced from break site. (C) The D-loop is nicked prior to extension of the invading end to create a single CO product and a broken arm of the donor chromosome (black). As shown, extension of the 3′ (red) end on the other side of the original DSB is templated from the intact sister chromatid. This provides homology to the broken donor and the reciprocal CO product is generated by an annealing reaction.