In the replication cycle of the Human Immunodeficiency Virus (HIV), which enzyme converts single-stranded viral RNA into double-stranded viral DNA inside the host cell cytoplasm?

Answer and explanation

Correct answer: D. Reverse transcriptase

  1. Step 1: HIV is an enveloped retrovirus possessing a single-stranded RNA genome and viral enzymes.
  2. Step 2: After the viral envelope glycoproteins () bind to CD4 receptors and coreceptors (CCR5/CXCR4) on helper T-lymphocytes or macrophages, the viral core enters the cytoplasm.
  3. Step 3: The viral RNA-dependent DNA polymerase (reverse transcriptase) transcribes the single-stranded viral RNA into a complementary cDNA strand, and then into double-stranded proviral DNA.
  4. Step 4: The proviral DNA is transported into the host nucleus, where viral integrase incorporates it into the host cellular genome.
Answer
Reverse transcriptase
Why not the others: 'RNA polymerase II' is a host enzyme that transcribes integrated proviral DNA into viral mRNA; 'DNA ligase' joins Okazaki fragments during host DNA replication; 'Integrase' catalyzes the insertion of viral DNA into the host chromosome.

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