(A) The smc6–9 alele and rtt107Δ mutant show decreased recombination between sister chromatids. Wildtype (CCG7802), rad55Δ (CCG7804), rtt107Δ (CCG7855) and smc6–9 (CCG7856) strains carrying the ade2-TRP1-ade2 recombination assay [27] were grown on YPD plates at 30°C. Five independent colonies were inoculated into 5 ml of YPD and grown overnight at 30°C. Cells were pelleted and re-suspended in 1 ml of sterile water. Serial dilutions were then plated on SC medium minus adenine and tryptophan, and incubated for 3–4 days, after which colonies were counted. Ade+Trp+ recombination frequencies are plotted on the y-axis. (B) Rtt107 phosphorylation is required for its role in spontaneous sister chromatid recombination. Wt (CCG7802), rtt107Δ and rtt107Δ containing wildtype RTT107 (CCG8214), phospho-mutant RTT107-AQ (CCG8215) and phospho-mimmetic mutant RTT107-DQ (CCG8216) (under the galactose inducible promoter GAL1-10) strains with the engineered ade2-TRP1-ade2 recombination assay were grown on YPD plates at 30°C. Five independent colonies were inoculated into 5 ml of YPD and grown overnight at 30°C. Cells were then transferred to YP galactose and expression of constructs was induced for 4 hours. Cells were pelleted and re-suspended in 1 ml of sterile water. Serial dilutions were then plated on SC galactose medium minus adenine and tryptophan, and incubated for 3–4 days, after which colonies were counted. Ade+Trp+ recombination frequencies are plotted on the y-axis.