Which side chain critical to DNA strand elongation is lacking in the nucleotide analog azidothymidine (AZT)?
A)the 5′ OH group
B)the 2′ OH group
C)the 3′ OH group
D)the triphosphate group

Question

Quizplus · Accepted Answer

The critical side chain lacking in AZT is the 3′ OH group. This group is essential for the formation of a phosphodiester bond with the adjacent nucleotide during DNA elongation. Without it, DNA polymerase cannot continue to add nucleotides to the growing strand, leading to termination of DNA synthesis. AZT is a nucleoside analog, which is incorporated into the DNA strand by cellular enzymes but lacks the 3′ OH group, thereby terminating DNA synthesis.

Which Side Chain Critical to DNA Strand Elongation Is Lacking