Figure 1.—

Diagram of the simulations of sister chromatid exchange (SCE) and loop deletions. (A) The rDNA loci were modeled as strings of symbols with uninserted units represented by 0, R1-inserted by 1, R2-inserted by 2, and double-inserted by 3. The outcome of recombination was determined by two parameters: the offset size (an integer between 1 and 4, 1 and 8, or 1 and 16 in the various simulations) and the crossover location (random in all simulations). (B) Loop deletions occur when part of a chromatid forms a loop and a crossover generates an extrachromosomal circle that is lost.