Table 2.
Mutant frequencies (lac+ mutants per 108 cells) in SOS-induced pairs of strains containing the lac operon in opposite (L and R) orientations and carrying plasmid pRW134 (umuD′C)
| Experiment | lac allele (mutation) | Relevant genotype | lac orientation | Lac+/108 | L/R ratio | (P value)* |
|---|---|---|---|---|---|---|
| 1 | CC104 (G⋅C→T⋅A) | mutL | L | 0.9 | 1.2 | (0.53) |
| R | 0.75 | |||||
| recA730, mutL | L | 4.7 | 0.36 | (0.003) | ||
| R | 13 | |||||
| mutL [pRW134] | L | 1.0 | 1.7 | (0.09) | ||
| R | 0.6 | |||||
| recA730, mutL [pRW134] | L | 7.6 | 0.18 | (<0.0001) | ||
| R | 43 | |||||
| 2 | CC105 (A⋅T→T⋅A) | mutL | L | 0.5 | 2.5 | (0.02) |
| R | 0.2 | |||||
| recA730, mutL | L | 5.3 | 0.095 | (<0.0001) | ||
| R | 56 | |||||
| mutL [pRW134] | L | 0.9 | 2.3 | (0.50) | ||
| R | 0.4 | |||||
| recA730, mutL [pRW134] | L | 17 | 0.11 | (<0.0001) | ||
| R | 151 |
The experiments were performed with strains of the MC4100 background (see Materials and Methods).
*
In parentheses, the P value indicating the significance of L vs. R frequency differences, calculated as described in Materials and Methods).