Deoxyribonucleotide synthesis: hydroxyurea: practice question

The best answer is B, Ribonucleotide reductase, which converts ribonucleoside diphosphates to deoxyribonucleoside diphosphates. Hydroxyurea quenches the tyrosyl free radical required by the R2 subunit of ribonucleotide reductase, lowering deoxyribonucleotide pools and slowing DNA synthesis in rapidly dividing cells.

Dihydrofolate reductase is inhibited by methotrexate and trimethoprim, not hydroxyurea.

Thymidylate synthase is inhibited by the metabolite of fluorouracil.

IMP dehydrogenase is the target of mycophenolate in guanine nucleotide synthesis.

It tests Deoxyribonucleotide synthesis: hydroxyurea in Biochemistry. In sickle cell disease it raises fetal haemoglobin, reducing sickling, and it also reduces neutrophil counts. Myelosuppression is its main toxicity.

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.