BIOC2: Week 10 - Pyrimidines

Which of the following serves as one of the nitrogen sources for the pyrimidine ring?

• glutamate

• carbamoyl phosphate

• asparagine

• glycine

The first 3 enzymes in the de novo pyrimidine synthesis pathway are coded for by ________________.

• UMPS gene

• CAD gene

• separate genes

A 42-year-old woman has been diagnosed with liver cancer and is being treated with 5-FU. 5-FU is successful in destroying the tumor cells because it blocks the production of which one of the following?

• THF

• dTMP

• UMP

• Methylcobalamin

• CTP

Orotic aciduria is a deficiency of one or both enzymes coded by the _________ gene. This results in ________ anemia.

• UMPS, megaloblastic

• UMPS, microcytic

• CAD, megaloblastic

• CAD, microcytic

What are the end products of pyrimidine catabolism? [can select multiple]

• b-hydroxybutyrate

• b-alanine

• uric acid

• b-aminoisobutyrate

Methotrexate (an older cancer treatment medication) can be used as first-line therapy for rheumatologic and psoriatic diseases. The side effects of methotrexate are caused by which one of the following vitamin deficiencies?

• pyridoxine

• biotin

• niacin

• folate

• thiamin

Thymine nucleotides are not synthesized directly by cells but indirectly from other pyrimidine deoxyribonucleotides.

All of the following statements regarding thymine nucleotide synthesis are true EXCEPT:

• dUMP is the immediate precursor for dTMP.

• The action of ribonucleotide reductase allows dUTP to serve as a substrate in DNA synthesis.

• Thymidylate synthase catalyzes the formation of dTMP from dUMP.

• N5, N10-methylene-THF is used as a cofactor.