Question

14.7 A number of antiviral drugs act by preventing viral DNA synthesis. These drugs are typically chemically similar to nucleotides with a modification. For example, the drug may contain all relevant components of a nucleotide, including a proper purine or pyrimidine base, but lack the 3' OH group. How would this modification allow this drug to prevent viral DNA synthesis?

A. Once inserted into a growing DNA chain, the drug will not be able to form a normal double-helix, as it lacks the five-carbon sugar.

B. The drug would not be able to base pair with the template strand, and thus it lacks the ability to be incorporated into a growing DNA chain.

C. Once inserted into a growing DNA chain, the drug will not be able to form phosphodiester bonds and the next nucleotide would not be incorporated

D. Without the 3' OH group, phosphates cannot attach to this drug, and thus it lacks the ability to be incorporated into a growing DNA chain.

Answer 1

Answer

Option C is correct i.e " Once inserted into the growing DNA chain, the drug will not be able to form phosphodiester bonds and next nucleotide would not be incorporated".

Explanation

As we know, during DNA synthesis the coming nucleotides are added to the free 3' OH end of the primer. So, for the nucleotide addition, free 3'OH group is required but if the drug lacks this group then it blocks the DNA synthesis.