Graduate Pharmacy Aptitude Test (GPAT) 2012 Solved Paper

Study the following statements on alkylating agents as antineoplastics:
[P] : They get converted to azindinium ions and bind to 7 th position −N atom of guanine of DNA base pairs
[Q]: Nitrogen mustards and Sulfur mustards belong to this class of drugs
[R] : They inhibit dihydrofolate reductase enzyme thereby inhibiting DNA synthesis
[S] : They chelate electropositive atoms present in the DNA thereby inhibiting DNA uncoiling
Choose the correct combination of statements.