5-Fluoroorotic Acid (5-FOA)

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5-FOA (C5H3FN2O) counter selects for ura+ strains. The non-toxic 5-FOA is converted into toxic 5-flurouracil (which blocks DNA replication) in yeast cells with a functional ura4 gene that normally synthesizes uracil. We can thus select for strains that are ura-.

  • Make a 100X stock solution of 5-FOA in DMSO by adding 100 mg/ml.
  • For use, use 1:100 (200 µl/9cm plate or 3µl/300µl in Deep Well Plate).
  • Stock solution is available in freezer 7.
  • Keep plates in fridge.

The method works with both minimal medium (with reduced amount of uracil) or YES, however according to a discussion on PombeList (16 Sept 2019) works better with rich medium. For a good protocol on how to use this with YES, see: Petersen & Russell