TABLE 1.
Relative increases in mutation rates in homonucleotide runs (A4, A5, A12, and A14 of lys2::insE alleles) and CAN1
| Strain genotype | Relative rate of mutationa (mutants vs wild type)b
|
||||
|---|---|---|---|---|---|
| A4 (−1) | A14 (−1) | A5 (+1) | A12 (+1) | Canr | |
| Wild type | |||||
| Absolute (109) | 0.4 | 186 | 1.1 | 140 | 240 |
| Relative | 1 (4/55)c | 1 (10/10)c | 1 (7/21)c | 1 (8/8)c | 1 |
| exo1 | 2.5 (4/34) | 97 (8/8) | 2 (19/29) | 2 (5/5) | 6.5 |
| msh2 | 77.5 (20/30)c | 9,460 (8/8) | 35 (16/30)c | 1,240 (8/8) | 27.4 |
| exo1 msh2 | 90 (14/22) | 8,980 (6/6) | 47 (16/21) | 544 (5/5) | 32.2 |
| pol2-4 | 6 (7/20)c | 2 (10/10) | 7 (13/27)c | 1 (10/10) | 2.3 |
| pol2-4 exo1 | 278 (29/38) | 925 (6/6) | 769 (33/35) | 116 (6/6) | 37 |
| pol2-4 msh2 | 2,870 (26/29)c | 23,390 (10/10) | 10,820 (30/30) | 2,040 (9/9) | 475 |
| pol2-4 exo1 msh2 | NDd | 16,666 | ND | 3,150 | 729 |
| msh3 | ND | 6 (6/6) | ND | 2 (6/6) | 2.0 |
| pol2-4 msh3 | ND | 15 (6/6) | ND | 2 (6/6) | 4.3 |
| msh6 | ND | 189 (7/7) | ND | 32 (7/7) | 9.2 |
| pol2-4 msh6 | ND | 317 (7/7) | ND | 60 (7/7) | 480 |
| msh3 msh6 | ND | 18,820 (6/6) | ND | 1,670 (6/6) | 29.2 |
| pol2-4 msh3 msh6 | ND | 46,450 (6/6) | ND | 3,170 (6/6) | 1,440 |
| pol3-01 | 37.5 (4/37)c | 54 (10/10) | 93 (19/22)c | 20 (10/10) | 44.2 |
The mutation rate in the run (Rr) was calculated as follows: Rr = Rt (Nr/Nt) where Rt is the total rate of reversion, which was determined from the median in a fluctuation test of more than 12 independent cultures (19). The fold increase in the mutation rate was determined as the ratio of the mutation rate of the mutant strain to the mutation rate of the wild-type strain. The nature of the Canr mutants was not determined. The Canr mutation rate was determined from the median in a fluctuation test of more than 12 independent cultures.
The ratio of the number of revertants with a frameshift mutation in the run (Nr) to the total number of revertants (Nt) analyzed by sequencing is given in parentheses. As observed previously (40) all the frameshift mutations in the A4 and A14 runs that were analyzed were due to −1 nucleotide deletions; all frameshift mutations in the A5 and A12 runs were due to +1 nucleotide insertions.
Data from the work of Tran et al. (40), with permission.
ND, not determined.