Question

Using the context provided in the passage, which of the following best explains why those seeking immunity against retroviruses would need to be constantly injected with vaccine?

a. because the reverse transcriptase of a retrovirus does not proofread and therefore genomic changes are expected.
b. because human immunity can only last one year without re-administration of a booster for the same shot.
c. because the complementarity of the viral double-stranded dna becomes compromised such that immune cells cannot recognize it.
d. because when the virus is outside of the body, transcription becomes altered due to a less processive rna polymerase.

Answer 1

The reverse transcriptase of a retrovirus does not proofread and therefore genomic changes are expected. Hence the correct option is a.

Retroviruses, like HIV, use reverse transcriptase to convert their RNA genome into DNA upon entering a host cell. Unlike cellular DNA polymerases, reverse transcriptase lacks proofreading activity, leading to a higher likelihood of errors during the conversion process. This lack of proofreading contributes to the high mutation rate observed in retroviral genomes.

Continuous injection of a vaccine is necessary in the context of retroviruses because the rapidly mutating nature of the virus allows it to generate diverse variants. Some of these variants may escape recognition by the immune system, potentially compromising the effectiveness of previously administered vaccines. Regular booster shots help the immune system stay updated and capable of recognizing and combating the evolving retrovirus variants, thus maintaining immunity over time. Hence the correct option is a.