Table 1.

Mutation rates in the LacZ gapped DNA forward mutation assay.

	WT		D402A		L606M		Exo−/Exo+ ratio
	Number detecteda	Error rateb (×10−5)	Number detected	Error rate (×10−5)	Number detected	Error rate (×10−5)
Total Plaques	43,615		18,004		12,216
Total Mutants	54		155		159
Mutant Frequency	1.2 × 10−3		8.6 × 10−3		13 × 10−3
Base Substitutions	26	≤0.45	69	4.4	73	6.7	7.2
+1 Insertions	9	0.077	30	1.2	42	2.4	≥9.8
−1 Deletions	13	0.11	51	2.0	45	2.6	16
Large Deletions	3	6.9 (MF)c	13	72 (MF)	7	57 (MF)	18
Other Mutationsd	2		2		1

^aThe total mutants reported may be greater or less than the sum of the different types of mutations because of the infrequent failure of a sequencing reaction, or the occasional presence of more than one distinct mutation in an individual plaque. Mutations were considered to be distinct as long as they were separated from each other by 3 or more nucleotides.

^bBackground mutation frequencies are 3.4 × 10⁻⁴ for base substitutions and 0.55 × 10⁻⁴ for single base insertions and deletions, corresponding to background error rated of 0.45 × 10⁻⁵ for base substitutions and 0.046 × 10⁻⁵ for single base insertions and deletions [21].

^cThe number of scorable sites for large deletion errors is not defined; therefore this value is given as a mutant frequency (MF) rather than an error rate.

^dOther mutations Pol δ were: WT, 2 occurrences of TTT to CTCT at +137 to +139; D402A, deletion of TA at −34 to −33, insertion of AC at −56 to −55; L606M, deletion of AC at −56 to −55.