The following questions refer to the following paragraph.
HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome from an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogues (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR.
-Within the body of an HIV-infected individual who is being treated with a single NA, and whose HIV particles are currently vulnerable to this NA, which of these situations can increase the relative fitness of the virus? 1. mutations resulting in RTs with decreased rates of nucleotide mismatch
2. mutations resulting in RTs with increased rates of nucleotide mismatch
3. mutations resulting in RTs that have proofreading capability
A)1 only
B)2 only
C)3 only
D)1 and 3
E)2 and 3

Question

Quizplus · Accepted Answer

If the HIV particles are vulnerable to a single NA, it means that the drug is effectively targeting the RT enzyme. Mutations resulting in RTs with decreased rates of nucleotide mismatch (Option 1) would decrease the overall replication fidelity and reduce the fitness of the virus. Mutations resulting in RTs that have proofreading capability (Option 3) would make the enzyme more accurate but slower, which would not be advantageous in the current scenario. However, mutations resulting in RTs with increased rates of nucleotide mismatch (Option 2) would make the virus more prone to mutations, which could increase the chance of developing drug resistance and potentially increase the fitness of the virus. Therefore, Option 2 is the best choice.

The Following Questions Refer to the Following Paragraph