Question

B. Below is the structure of the nucleoside analog azidothymidine (AZT). AZT was used as an early HIVIAIDS therapy that inhibited replication by the human immunodeficiency virus (HIV) by blocking synthesis of viral DNA. NH HO i) (2 points) Before its incorporation into viral DNA, AZT is converted in the cell to the nucleoside triphosphate. Draw the structure of azidothymidine triphosphate with all ionizable groups in the ionization states expected at pH 7. (Note: the azido group will appear at pH 7 as shown in the figure). li) (3 points) HIV has an RNA genome. To successfully infect a cell, it must synthesize a complementary DNA strand. Explain why DNA synthesis is terminated when AZT is incorporated into the complementary DNA strand in place of thymidine.

Answer 1

H C O-H

when it incorporates into complementary DNA strand it doesnot contains 3' OH group to attach to the next 5' phosphate group so no nucleotide will make phosphodiester bond with the AZT and DNA synthesis will be terminated.