IRA deletion strains are sensitive to cdc13-1-induced arrest despite an intact DNA damage checkpoint. (A) 10-fold serial dilutions were spotted to YPD agar and incubated at the indicated temperature for three days. (B) Log phase cultures were sonicated, spread onto 30° YPD agar and incubated at 30° for 8 hours. 100 colonies were scored for each strain. Values are mean ± standard deviation of three independent assays. (C) Cultures were arrested with α-factor at 21°, then raised to 32° to inactivate cdc13-1, then released from the α-factor block at 32°. Samples were sonicated, counted, serially diluted, and plated to 21° YPD agar. Viability is calculated as (CFU/mL)/(Total cells per mL) normalized to α-factor samples. Values are mean ± standard deviation of three assays. **p < 0.01, ***p < 0.001 by student's t-test. (D) YPD plates from (C) were inspected 18 hours after returning to 21°. Between 50 and 60 colonies were scored for each strain. Values are mean ± standard deviation of three assays.