Respiration competence of daughter cells could be inferred from their growth rate and was confirmed by replica plating to media containing a non-fermentable carbon source (data not shown). The upper panel was photographed 2 days after placement of last daughter, while the lower panel was photographed 10 days after placement of last daughter. B) A comparison of the age of onset for the subpopulation of mother cells that lose the ability to produce daughters with respiratory function. (TIF) Figure S2 Preparation and normalization of ERC southern blotting. ERC Southern blot of total genomic DNA isolated from wild type cells and digested with BamHI and with or without RecBCD. Arrow indicates the linear rDNA array. (EPS) Yeast strains used in this study. Table S1 (DOC) References 1. DePinho RA (2000) The age of cancer. Nature 408: 248–254. 2. Renan MJ (1993) How many mutations are required for tumorigenesis? Implications from human cancer data. Mol Carcinog 7: 139–146. 3. 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