TABLE 1.

Rates of mutation in the mitochondrial genome

	% petites	Rate of eryR	Rate of microsatellite instability	Rate of direct repeat-mediated deletion
Wild-type	0.35	2.0 × 10−8	6.5 × 10−7	0.7 × 10−4
abf2-Δ	81	2.1 × 10−8 (1.1-fold)	4.0 × 10−6 (6-fold, P = 0.01)	3.6 × 10−4 (5-fold, P < 0.0001)

The percentage of petite cells was determined by selecting respiring cells in glycerol medium (YPG), then isolating independent colonies on synthetic dextrose medium to release selection. For each experiment, at least 20 independent colonies were resuspended in sterile water and appropriate dilutions were plated on YPG + 0.1% dextrose. Petite and grande colonies were scored after 4 days incubation at 30°. The rate of erythromycin resistance (ery^R) was determined as described (Mookerjee and Sia 2006). To measure the rate of microsatellite instability, independent colonies containing the reporter were grown with glycerol selection for 3 days at 30°, resuspended in sterile water, and appropriate dilutions were plated on YPG to determine the number of respiring cells, and synthetic dextrose medium lacking arginine (SD −Arg), to select for reversion of the ARG8^m frameshift. Arg⁺ colonies were scored after 7 days at 30°. Rates of DRMD were determined similarly: strains were grown for 2 days on SD −Arg to select the reporter; independent colonies were isolated on SD medium and allowed to grow for 3 days at 30°. Cells from 20 independent colonies were resuspended in sterile water and appropriate dilutions plated on YPG and SD −Arg. Recombinants were scored on YPG after 3 days at 30°. All experiments were performed at least three times. All rates were calculated by the method of the median (Lea and Coulson 1949), and two-tailed P-values were calculated using an unpaired t-test performed by Instat3 for Macintosh (GraphPad Software).