For some reason, direct selection on G418 plates after transformation often yields false positives.

To minimize the chance of picking false positive clones after G418 selection, use the following procedure:

- Transform your plasmid into the yeast strain of choice, using any available method
- After the heat shock, spin down the cells
- Resuspend the pellet in 2xYPAD medium
- Incubate at 30?C with mild shaking for 90 minutes (recovery period)
- Plate a 1:5 dilution on one 10 cm YPAD plate and the remainder on another 10 cm YPAD plate (both supplemented with 200 ug/ml G418)
- Incubate at 30?C for 3-4 days
- Pick only large colonies, the small ones may represent background. After 3-4 days, your colonies should have a diameter of at least 2 mm
- Pick several colonies and restreak them onto fresh YPAD/G418 plates
- Grow for 2 days at 30?C
- Only take those colonies which show robust growth