Spontaneous mutation rates determined by the method of the median after galactose induction of the apn1Δ strain BGY113 containing plasmid pYES, pYES plus YEpAPN1 (which expresses APN1), pYES-MAG, or pYES-MAG plus YEpAPN1. The values reported are the mean ± standard deviation. (Inset) Replotted data for pYES, pYES plus YEpAPN1, and pYES-MAG plus YEpAPN1.