(A) Induction of recombination by ionizing radiation of nocodozole-arrested WT, MCD1 and SMC3 simplex cells and stationary WT and MCD1 simplex cells. After irradiation, cells were plated to synthetic complete (SC) or SC lacking tyrosine (SC-Tyr) and incubated for 2–3 days. Shown are the net recombination frequencies (induced minus “no irradiation”). (B) IR-induced recombination in nocodazole arrested MCD1 duplex cells (as a comparison, the WT data was pooled from panel A and four more WT cultures that were done side-by-side). (C) UV-induction of recombination in nocodozole-arrested and stationary WT and MCD1 simplex cells. (D) Induction of recombination by hydroxyurea. Logarithmically growing WT or MCD1 simplex cells were treated with HU overnight. Cells were then spread on complete and Tyr⁻ plates. Presented are induced recombination frequencies (the frequency measured after HU treatment minus the frequency measured without treatment; see legend to Figure S5 for a detailed description). Recombination frequencies were obtained from at least 8 cultures for each genotype and for each DNA damaging agent.