Table 1. Stable Lac⁺ revertants formed under selection (39 mutations).

Number of mutations	Mutation that corrects lacIZ reading frame	Site of mutation in lacIZ gene	Sequence changes in the lacI region and revertant numbers
25	Single base –1	In original mutant run	gagacggggca - > gagacgggca S1,S4,S6,S7,S9,S10,S11,S14,S16,S19,S20,S21,S23,S25,S26,S27,S28,S29,S30,S32,S33,A58,A60,A61,A62
7	Single base –1	Sites near original mutant run	TG->T (A57a, A59a), GC->G(S2, S31), AG->A(S24a), CA->(S13), GT->G(S22a)
3	Multi-base insertions	Sites near original mutant run	+2 bp C->CGT (S34), +5 bp T->TTCACC (S5), +8 bp T->TTTCACCAG (S15)
4	Multi-base deletions	Sites near original mutant run	−7 bp(S12), -10 bp(S3), –112 bp (S17, S18) removes original site; between repeated GGTTTGC

^aRevertants that arose by losing a single base from a monotonous run of three or more bases.