(A) Schematic representation of the YMV45 chromosome III region, where a unique HO-cut site is adjacent to the leu2::cs sequence, which is 4.6 kb apart from the homologous leu2 sequence. HO-induced DSB results in generation of 12 kb and 2.5 kb DNA fragments (HO-cut) that can be detected by Southern blot analysis with a LEU2 probe of KpnI-digested genomic DNA. DSB repair by SSA generates a product of 8 kb (SSA). K, KpnI. (B) Exponentially growing YEPR cell cultures of YMV45 derivative strains were transferred to YEPRG. Southern blot analysis of KpnI-digested genomic DNA. (C) Densitometric analysis of the SSA product. Plotted values are the mean values of three independent experiments as in panel B, with error bars denoting s.d. (D) Percentage of colony formation on YEPRG plates relatives to colony formation on YEPD plates. The reported values are the mean values of three independent experiments, with error bars denoting s.d. ***P<0.005, t-test.