HIV — MCQs

Question 1: Four scientists were trying to measure the effect of a new inhibitor X on the expression levels of transcription factor, HNF4alpha. They measured the inhibition levels by using RT-qPCR. In short they converted the total mRNA of the cells to cDNA (RT part), and used PCR to amplify the cDNA quantifying the amplification with a dsDNA binding dye (qPCR part). Which of the following group characteristics contains a virus(es) that has the enzyme necessary to convert the mRNA to cDNA used in the above scenario?

• A. Enveloped, dimeric (+) ssRNA (Correct Answer)
• B. Enveloped, circular (-) ssRNA
• C. Nonenveloped, (+) ssRNA
• D. Nonenveloped, ssDNA
• E. Nonenveloped, circular dsDNA

Explanation: ***Enveloped, dimeric (+) ssRNA*** - This group describes **retroviruses**, which possess the enzyme **reverse transcriptase**. - **Reverse transcriptase** is essential for converting their **RNA genome** into **cDNA**, a process analogous to the RT step in RT-qPCR. - Examples include **HIV**, which is tagged to this topic. *Enveloped, circular (-) ssRNA* - This description does not accurately represent a major viral family. - Most enveloped negative-sense RNA viruses have **linear or segmented genomes** (e.g., **Orthomyxoviruses**, **Bunyaviruses**), not circular. - These viruses replicate using an **RNA-dependent RNA polymerase** to synthesize mRNA from their negative-sense RNA genome. - They do not inherently carry or require **reverse transcriptase** for their life cycle. *Nonenveloped, (+) ssRNA* - These viruses, like **Picornaviruses**, directly use their positive-sense RNA as mRNA and replicate via an **RNA-dependent RNA polymerase**. - They do not possess **reverse transcriptase** for cDNA synthesis. *Nonenveloped, ssDNA* - Viruses with a **single-stranded DNA genome**, such as **Parvoviruses**, replicate by first synthesizing a double-stranded DNA intermediate. - Their replication machinery does not involve **reverse transcriptase** to convert RNA to DNA. *Nonenveloped, circular dsDNA* - Viruses in this group, like **Papillomaviruses** and **Polyomaviruses**, have a circular double-stranded DNA genome and replicate within the host nucleus using the host's DNA polymerase. - They do not utilize or encode **reverse transcriptase** for their replication cycle.