mutations can occur after cells are plated on canavanine medium. (A) Cultures incubated on canavanine plates produced
can1 mutant colonies, some of which were very small (black arrowheads). (B) ‘‘Large’’ colony data from .200 independent cultures fit Luria-Delbru¨ ck
distribution (L-D) better than Poisson distribution, while ‘‘small’’ colony data fit Poisson better than L-D. Correlation coefficients between data and
theoretical distributions that best fit the data are shown. (C) Reconstruction experiment demonstrating that small canavanine-resistant colonies are
not inherently slow growing. All of the can1 colonies originated from seeded can1 cells and all gave rise to large colonies, irrespective of whether
they originally came from large or small can1 colonies. (D) NHEJ and DNA polymerase f affect canavanine-induced mutagenesis. yku80D reduced
post-plating mutation (right panel) while leaving mutation in culture unaffected (left panel), while rev3D reduced both CAN1 mutation in culture and
post-plating. Error bars represent 95% confidence intervals for mutation rates in culture and standard deviations for post-plating mutation
frequencies (*, P,0.05, Student’s t-test).
doi:10.1371/journal.pgen.1003680.g001