Figure 1.

Protocol to detect pol β mutator mutants carrying a randomly mutagenized pol β cDNA are picked into Luria–Bertani broth containing 1 mM isopropyl β-d-thiogalactopyranoside and grown in 24-well microtiter plates overnight at 37°C. Aliquots of each well are spread onto Eglu agar and incubated for 3 days at 30°C. In this assay the pol β-WT strain produces 0–1 Trp⁺ revertants and mutator mutants such as pol β-14, -5, and -166 produce greater than 10 Trp⁺ revertants.