How are cancer therapies tailored to nucleotide synthesis - explain using the example of fluorouracil and methotrexate.

By preventing the synthesis of DNA halting cell growth.

Explanation:

Fluorouracil and methotraxate prevent the synthesis of the neucleoside Thymidine thus preventing DNA replication and elongation. Methotraxate has a structure analogous to Folic acid which is important for thymidine synthesis. Thus, it acts as a competitive inhibitor on dihdrofolate reductase an enzyme that is essential for tetrahydrofolate formation, a folic acid derivative.

Fluorouracil acts by inhibiting thymidylate synthase which catalyses an essential step in Thymidine synthesis.