Read the passage and answer the following questions:
Once inside the human body, the HIV virus enters macrophages, a type of immune cell. Within the macrophages, the viral RNA genome is replicated to form viral DNA with the assistance of an enzyme called reverse transcriptase. This viral DNA is then integrated into the DNA of the host cell, directing the infected cell to produce virus particles. The infected macrophages continue to produce the virus, acting as HIV factories. Simultaneously, the HIV virus also enters helper T-lymphocytes (TH cells) and replicates within them, producing new viruses. These progeny viruses are released into the bloodstream and target other helper T-lymphocytes, leading to a progressive decrease in their numbers. As the number of helper T-lymphocytes decreases, the infected person experiences various symptoms such as fever, diarrhoea, and weight loss. Due to the decrease in helper T-lymphocytes, the person's immune system becomes severely weakened, making them susceptible to infections that could typically be overcome, including those caused by bacteria, such as Mycobacterium, viruses, fungi, and parasites like Toxoplasma. The patient becomes immunodeficient, unable to effectively protect themselves against these infections. Enzyme-linked immunosorbent assay (ELISA) is a widely used diagnostic test for AIDS, allowing for the detection of HIV infection. While antiretroviral drugs can partially prolong the life of AIDS patients, they cannot prevent death, which is inevitable without a cure for the disease. As AIDS has no cure, prevention is the best option. HIV infection primarily spreads through conscious behavioural patterns, unlike infections like pneumonia or typhoid that may occur inadvertently. Steps such as ensuring blood safety in blood banks, using disposable needles and syringes, promoting condom distribution, controlling drug abuse, advocating safe sex, and regular HIV check-ups in susceptible populations are taken to prevent the spread of HIV infection. It is essential not to hide HIV infection or AIDS as doing so may lead to further transmission. HIV/AIDS-infected individuals deserve help and sympathy from society instead of being stigmatized. Recognizing HIV/AIDS as a collective problem and taking collaborative actions between society and the medical fraternity are needed to prevent the widespread dissemination of the disease. It requires a joint effort to tackle this malady and prevent its spread.
What enzyme assists in replicating the viral RNA genome of HIV into viral DNA within macrophages?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Reverse transcriptase
The passage states that “Within the macrophages, the viral RNA genome is replicated to form viral DNA with the assistance of an enzyme called reverse transcriptase”.
Making DNA from an RNA template is the reverse of the usual transcription (DNA to RNA). The enzyme that does this is therefore called reverse transcriptase. HIV is a retrovirus, and this enzyme is the mark of such viruses.
Option (1) DNA polymerase — Incorrect. DNA polymerase makes DNA on a DNA template. It cannot copy the RNA genome of HIV into DNA.
Option (2) Reverse transcriptase — Correct. Reverse transcriptase copies the viral RNA genome into viral DNA inside the macrophages.
Option (3) RNA polymerase — Incorrect. RNA polymerase makes RNA on a DNA template, the opposite of the step asked.
Option (4) Integrase — Incorrect. The passage says the viral DNA is then incorporated into the host DNA, but it does not name any enzyme for that step, and integrase does not make DNA from RNA.