Arrange the following steps involved in replication of retrovirus in correct sequence.
(A) Viral RNA is introduced into the animal cells
(B) Viral DNA incorporated into the host genome
(C) New viral RNA is produced by the infected cell
(D) Viral DNA is produced by the reverse transcriptase
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (D), (B), (C)
(A) Viral RNA is introduced into the animal cells — comes first. A retrovirus such as HIV has an RNA genome. It enters a cell (a macrophage in HIV) and releases this RNA.
(D) Viral DNA is produced by the reverse transcriptase — comes second. The enzyme reverse transcriptase copies the RNA genome into viral DNA. This is the reverse of the usual flow of information from DNA to RNA.
(B) Viral DNA incorporated into the host genome — comes third. The viral DNA can be joined into the DNA of the host cell only after it has been made.
(C) New viral RNA is produced by the infected cell — comes last. The host DNA now carries the viral genes, so the infected cell is directed to produce virus particles, and new viral RNA is made.
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NCERT Extract:
AIDS – …
Figure 7.6 Replication of retrovirus