Figure 5.

A DSB repair scenario consistent with the transitions in sectored colony 2. Red and black lines represent single strands of W303 and YJM chromosomes, respectively. Both red sister chromatids are broken, and the first repair event is resolved as a CO. Each of the hetDNA tracts (yellow boxes) that flank the DSB is repaired as a GC (gray boxes). The second repair event uses either the CO-resolved sister chromatid or the NCO chromatid of the homolog as a template. Repair using the sister chromatid is shown, and SDSA is assumed to be the repair mechanism because there is a GC tract on only one side of the initiating DSB. Because the hetDNA correction results in a GC tract that is longer than that on the CO chromosome, the nonsister CO chromatid is excluded as a repair template. For this particular sectored colony, the NCO event could have preceded that of the CO event or both could have occurred at the same time. In this case, both repair events would have involved the homolog.