Question

Provirus is the name of
(a) Free virus
(b) Free DNA
(c) Primitive virus
(d) Integrated viral genome

Answer 1

Hint: A provirus is a DNA molecule that enters into the host cell and is attached to its genome. In the case of bacterial viruses or bacteriophages, their proviruses are often known as prophages. It can be a state of virus replication or a stage that persists for a longer time.

Complete answer:
A provirus is a viral genome that is integrated with the host cell DNA. This provirus state can be seen as a stage of virus replication, or as a state that persists over long periods of time in the form of either inactive viral infections or as endogenous viral elements.
- In the case of inactive viral infections, the virus does not replicate itself except through the replication of its host cell as the DNA is integrated with the host genome. This state may persist over many generations of the host cell.
- A provirus does not make new DNA copies directly to replicate itself while being integrated into the host genome.
- Instead, a provirus passively replicates along with the host cell genome and is thus passed on to the next generation of the original host cell.
- Thus, all descendants of the infected cell will ultimately bear the proviruses in their genomes and then they keep on passing the genome to several generations.
- This process is also known as lysogenic viral reproduction.
So, the correct answer is, ‘(d) Integrated viral genome’.

Note:
- Endogenous retroviruses are always present in the provirus state. When a retrovirus invades a host cell, the RNA is reverse- transcribed into DNA by reverse transcriptase which is then inserted into the host genome by enzyme integrase.
- In bacteriophages, it is important to note that proviruses are different from prophages as unlike prophages, proviruses do not separate themselves back from the host genome when the host cell is stressed.