A diagram of HIV replication shows the virus entering a macrophage. Arrow 1 shows the viral RNA being copied into viral DNA by enzyme X. Arrow 2 shows the viral DNA entering the host DNA, after which the cell keeps producing viruses. New viruses then attack cells Y, whose numbers fall progressively. Which identification is correct?
Show the answer
After entering a macrophage, HIV's RNA genome is copied into viral DNA by reverse transcriptase and incorporated into host DNA, so the macrophage keeps producing virus. HIV then enters helper T-lymphocytes, whose number progressively decreases.
- A.
Viral DNA is made from RNA by reverse transcriptase, and HIV mainly attacks helper T-cells.
- B.
Ligase joins DNA fragments; the progressively falling cells are helper T-lymphocytes.
- C.
HIV attacks helper T-lymphocytes, not red blood cells.
NCERT: Class 12 Biology, Chapter 7, 7.3