TABLE 3.

Base changes in leu revertants of the ΔmutSL strain^a

Revertant allele (day of expt)	Revertant sequenced	Position of mutation	Type of mutation	DNA change (result of mutation)
leuC (5)	1	346	Transition	G→A (Gly→Ser)
	2	359	Transversion	C→A (Pro→Glu)
		427	Transition	A→G (Arg→Gly)
	3	427	Transition	A→G (Arg→Gly)
leuC (6)	4	427	Transition	A→G (Arg→Gly)
	5	?	?	?
	6	427	Transition	A→G (Arg→Gly)
	7	363	Transition	G→A (Gly→Glu)
	8	427	Transition	A→G (Arg→Gly)
leuC (7)	9	427	Transition	A→G (Arg→Gly)
	10	427	Transition	A→G (Arg→Gly)

^aChromosomal DNA was isolated (11) from Leu⁺ revertant colonies of the mutSL strain collected from plates of adaptive mutagenesis assays during day 5, 6 or 7. A 303-bp fragment encompassing nucleotides 353 to 655 of the leuC ORF was amplified by PCR and sequenced as described in Materials and Methods. ?, mutations were not found in the sequenced leuC gene.