The synthetic pyrimidine analog 5-fluorouracil (5-FU) is an antimetabolite drug that has been widely used for the treatment of various types of cancer like colon, breast, and other cancers through meddling with the cellular biosynthetic activity via inhibiting thymidylate synthase or by misincorporation of its metabolites into nucleic acid [9]. The gene discussed is TYMS; the disease is cancer.