Table 3.
Calculation of the size of the hypermutating subpopulation and its increase in mutation rate
| Phenotype | Cells, no. | Cell-days | Mot−, no. | Mot− per cell, % | Mot− per cell-day, % |
|---|---|---|---|---|---|
| Lac− zeros | 2,878 | 6,990 | 2 | 0.07 | 0.029 |
| Lac+ singles | 3,168 | 7,006 | 48 | 1.5 | 0.68 |
| Lac+ doubles | 13 | 34 | 2 | 15 | 5.9 |
p and M calculations are as follows.
R1/0 = 0.68/0.029 = 24.
R2/0 = 5.9/0.029 = 203.
p = R1/0/(R2/0)2 = 24/4.2 × 104 = 5.7 × 10−4.
M = R2/0[1 − (pR2/0)] = 203/(1 − 0.12) = 231.
Proportion of single mutants that arise from the hypermutating subpopulation,
pM/[pM + (1 − p)] = 0.13/[0.130 + (1 − 5.7 × 10−4)] = 0.12.
Proportion of double mutants that arise from the hypermutating subpopulation,
pM2/[pM2 + (1 − p)] = 30/[30 + (1 − 5.7 × 10−4)] = 0.97.