WT and apn1/2 haploid strains growing in YPDA were arrested at G2/M by nocodazole and treated with 0.1% (11.8 mM) MMS for 15 min in PBS. Cells were returned to YPDA containing nocodazole and incubated for up to 16 hours (30°C). Cells were collected and processed for PFGE analysis. Following PFGE, chromosomes were visualized by ethidium bromide staining. The letter “C” above the first lane stands for mock-treated control samples (the same applies to the rest of the figures). The slow moving DNA (SMD) in the apn1/2 mutant is detected as a wide band of DNA between the largest chromosome (Chr XII) and the wells following treatment.