TABLE 2.

Colony mutation frequencies for various Mg²⁺ and dNTP concentrations in plasmid-based lacZα complementation assay

Total Mg2+ (free Mg2+) (mM)a	Total dNTPs (μM)	No. of white and faint blue colonies	Total no. of colonies	CMF (×10−3)	CMF − Bkg (×10−3)c	Relative fidelityd	P valuee
—b	—b	17	10,138	1.7
6 (5.6)	100	71	4,328	16	14	1
2 (1.98)	5	27	2,866	9.4	7.7	1.9	0.0066
2 (1.6)	100	117	12,602	9.3	7.6	1.9	<0.0001
1.5 (1.1)	100	51	5,983	8.5	6.8	2.1	<0.0001
1 (0.6)	100	54	6,492	8.3	6.6	2.1	<0.0001
0.25 (0.24)	5	19	5,195	3.7	2.0	7.0	<0.0001

^aFree Mg²⁺ was calculated as described in Materials and Methods using the dissociation constant for Mg²⁺ and ATP.

^b—, background was determined by transfecting plasmids with unfilled gaps into bacteria. CMF was defined as white and faint blue colonies divided by total colonies. Refer to Results and Materials and Methods for details.

^cCMF − Bkg, frequency minus the background frequency from the first row (see footnote b).

^dAll values are relative to the 6 mM Mg²⁺/100 μM dNTP CMF − Bkg value (0.014). The 0.014 value was divided by the CMF − Bkg value for each condition to determine relative fidelity. Higher numbers indicate greater fidelity.

^eValues were calculated using a chi-square analysis after performing the background correction by subtracting (0.0017 × total colonies) from the white and faint blue colonies for each condition. All values were scored against that for the 6 mM Mg²⁺/100 μM dNTP condition.