Dominant-Negative Mutant Screen:

A total of 160 transformants—60 from the second gap repair transformation and 100 from the third gap repair transformation—were screened for inhibited growth on galactose containing media. The transformants were patched onto C-ura media and then replica plated:
1C-ura,
2C-ura+2%gal
3C-ura+4%gal
4complete.

In order to dilute out any glucose that may have remained after the initial replica plating, the C-ura+2%gal plates were replicated once more:
1C-ura,
2C-ura+2%gal
3C-ura+2%gal
4C-ura+4%gal
5complete.

After the initial replica plating five transformants showed no growth on the galactose containing media and two transformants displayed growth that was significantly slower than the control (transformant with the unmutagenized plasmid pBM258T/YTM1). All of these transformants came from the third gap repair transformation. After the second round of replica plating, additional slow-growing mutants were seen: one grew significantly slower than the control and four grew slightly slower than the control. There was no difference in rate of growth of any of the transformants on media containing 2% galactose or 4% galactose. These eleven mutants were chosen to be further studied.