NEET PG Medical – 2020 – Question -52
Which of the following drugs act by inhibiting DNA replication?
a) 6 Mercaptopurine
b) Actinomycin D
c) Mitomycin C
d) Asparaginase
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Correct Answer – A
Ans: A. 6 Mercaptopurine
6-Mercaptopurine acts by inhibiting DNA replication.
Antimetabolites:
- These are analogues related to the normal components of DNA or of coenzymes involved in the nucleic acid synthesis.
- They competitively inhibit the utilization of the normal substrate or get themselves incorporated forming dysfunctional macromolecules.
Includes: - Folate antagonist – Methotrexate (Mtx)
- Purine antagonist – 6-Mercaptopurine (6-MP)
- Pyrimidine antagonist – 5-Fluorouracil (5-FU)
Purine antagonists - Mercaptopurine (6-MP) and thioguanine (6-TG).
- These are highly effective antineoplastic drugs.
- After synthesis in the body to the corresponding mono ribonucleotides, they inhibit the conversion of inosine monophosphate to adenine and guanine nucleotides that are the building blocks for RNA and DNA.
- There is also feedback inhibition of de novo purine synthesis.
- They also get incorporated into RNA and DNA which are dysfunctional.
Ref: K. D. Tripathi 7th Edition. Page. 858, 862 – 863
