- 5-Fluorouracil is converted to 5-fluoro-2-deoxyuridylic acid (FdUMP), which inhibits thymidylate synthase and blocks DNA synthesis.
- FdUMP is responsible for the drug’s action in chemotherapy, specifically targeting rapidly dividing cancer cells.
5-Fluorouracil does not act on its own, it first has to be converted through the pyrimidine salvage pathway into an active nucleotide metabolite before it can interfere with DNA synthesis. Getting the name of that metabolite right comes down to two details: where the fluorine sits on the ring, and what kind of sugar is attached.
5-Fluorouracil carries its fluorine at the 5-position of the uracil ring, that is where the name comes from in the first place, so any option describing the fluorine at position 3 cannot represent this drug's metabolite. That rules out both the 3-fluoro-3-deoxy and 3-fluoro-3-oxy options right away.
The remaining detail is the sugar. The active metabolite is built on a 2-deoxyribose sugar, the same sugar found in DNA nucleotides, not a plain (oxy) ribose. So a name using 'oxy' at the 2-position, rather than 'deoxy,' does not match either.
Once the fluorine is placed correctly at position 5 and the sugar is correctly identified as 2-deoxy, the name that fits is 5-fluoro-2-deoxyuridylic acid, which is the compound (FdUMP) that blocks thymidylate synthase and stops DNA synthesis in dividing cells.
That makes 5-fluoro-2-deoxyuridylic acid the correct answer.
| Disease | Diagnostic tests | ||
|---|---|---|---|
| P. | Tuberculosis | (i) | Lepromin test |
| Q. | AIDS | (ii) | ELISA |
| R. | Syphilis | (iii) | Mantoux test |
| S. | Leprosy | (iv) | Kahn's test |