5F-UMP is further activated into 5-fluoro-2′-deoxyuridylate, known to be a potent inactivator of thymidylate synthase (TS), the obligate source of dTTP for DNA synthesis in malaria parasites since unlike the host cell, the parasite cell is unable to salvage preformed pyrimidines. The gene discussed is TYMS; the disease is malaria.