After getting into the body of a person, HIV enters ...A..., where its RNA genome replicates to form viral DNA with the help of the enzyme ...B.... These cells continue to produce virus and act like an HIV factory. Simultaneously, HIV enters ...C..., replicates and produces progeny viruses.
Here A, B and C refer to:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A–macrophages, B–reverse transcriptase, C–helper T-lymphocytes
HIV is a retrovirus with an RNA genome. To multiply, it must first copy its RNA into DNA, which then joins the host cell’s DNA. The infection goes in two steps, first in one type of cell and then in another.
Blank A – macrophages. HIV first enters macrophages. These cells keep making virus and act like an HIV factory. Helper T-lymphocytes are infected next, and B-lymphocytes are not the cells named in this step.
Blank B – reverse transcriptase. Making DNA from an RNA template is reverse transcription, done by reverse transcriptase. RNA polymerase makes RNA from DNA, and DNA polymerase copies DNA from DNA, so neither can form viral DNA from the RNA genome.
Blank C – helper T-lymphocytes. At the same time HIV enters helper T-lymphocytes (TH), multiplies and releases new viruses. These go on to attack more TH cells, and their number falls steadily.
NCERT Extract:
AIDS – “… After getting into the body of the person, the virus enters into macrophages where RNA genome of the virus replicates to form viral DNA with the help of the enzyme reverse transcriptase. This viral DNA gets incorporated into host cell’s DNA and directs the infected cells to produce virus particles (Figure 7.6). The macrophages continue to produce virus and in this way acts like a HIV factory. Simultaneously, HIV enters into helper T-lymphocytes (TH), replicates and produce progeny viruses.”