5-Fluoroorotic acid (5FOA) is a fluorinated derivative of the pyrimidine precursor orotic acid. It is used in yeast genetics to select for the absence of the URA3 gene, which encodes the enzyme for the decarboxylation of 5-fluoroorotic acid to 5-fluorouracil, a toxic metabolite.

Useful in the identification and selection of the strains of Saccharomyces cerevisiae that contain the mutant ura3- gene. 5-FOA is toxic to yeast cells that can synthesize the enzyme orotidine-5'-phosphate decarboxylase and are therefore unable to grow on 5-FOA-containing media. Alternate Nomenclature: FOA, 5-FOA,...