| After the incubation period, the number of revertant colonies per plate is counted. |
| This gives the appearance of directed mutagenesis because only revertant cells survive mutagenesis. |
| No concentration-related increase of number of revertant colonies treated with cordycepin was observed. |
| If the same maximum copy number is used, there will also be a distinct effect on the fitness relative to revertant cells. |
| The number of visible revertant colonies was counted. |
| Cytotoxicity may be detected by a reduction in the number of revertant colonies, a clearing or diminution of the background lawn, or the degree of survival of treated cultures. |
