Question

In the given flow diagram, the replication of retrovirus in a host is shown.
Observe and answer the following questions.

a. Fill in (1) and (2).

b. Why is the virus called retrovirus?

c. Can the infected cell survive while viruses are being replicated and released?

Answer 1

Replication of the HIV virus

The following steps are taken by HIV to enter and cause infection in the human:-

• HIV enters the macrophage.
• The RNA genome of HIV using reverse transcriptase, gets reverse transcribed into viral DNA.
• The viral DNA gets incorporated into the DNA of the host cell.
• HIV uses the macrophage's machinery to produce many viral particles.
• Simultaneously, HIV infects T helper lymphocytes where the production of new viral particles begins.
• The progeny viruses get released into the blood by the lysis of the T helper cells.
• New T cells are further infected causing a decrease in the number of the lymphocytes.

Summary

Replication of retrovirus in host cell


Final answer

1: Viral DNA is produced
2: New viral RNA


Retrovirus

The genetic material of HIV virus is ssRNA. This gets reverse transcibed to form viral DNA with the help of reverse transcriptase.
Genetic information usually flows from DNA to RNA to proteins (Central Dogma), but in case of retrovirus, it is decoded backward initially and hence, the name retrovirus.

Final answer

Since the virus does not follow central dogma, hence, known as a retrovirus.


Survival of infected cells

The viral DNA gets incorporated into the host cell's DNA and directs the infected cells to produce virus particles. Infected cells survive while the viruses are being replicated. This is evident as the virus uses the host cell machinery for their replication.

Final answer
Yes