Fig. 2. Phenotypes of class I and class II mutants. Reporter strain GCY23 was transformed with plasmids (GLC16 or derivatives) containing the SIR2 mutant alleles indicated, SIR2 wild type or no SIR2 insert (vector). Ten-fold serial dilutions of cells were plated on SC-Leu+FOA (to measure TPE), SC-Leu-Trp (HMR silencing), Pb²⁺/G418 (rDNA silencing) and SC-Leu (total number of plasmid-containing cells).