Human Health And Disease

HIV, the causative agent of AIDS, is a retrovirus that carries single-stranded RNA as its genetic material along with the enzyme reverse transcriptase, which synthesises a complementary DNA copy from the viral RNA template inside the host cell. This newly made viral DNA then becomes incorporated into the host cell's genome and directs the production of new virus particles, making reverse transcriptase essential for the virus's life cycle and a key drug target. DNA polymerase III is incorrect because it is a bacterial enzyme involved in replicating the host's own DNA, not in converting viral RNA into DNA. RNA polymerase is wrong since it transcribes DNA into RNA, the opposite direction of the flow required here. Restriction endonuclease is incorrect because it is a bacterial defence enzyme that cuts DNA at specific sequences and plays no role in HIV genome integration. As described in NCERT Class 12, Chapter 8 (Human Health and Disease), HIV chiefly attacks helper T-lymphocytes, progressively weakening immunity. As a mechanistic check, only reverse transcriptase can perform the RNA-to-DNA conversion that defines retroviruses, confirming it as the correct enzyme responsible for integrating HIV into host DNA.