Question

What are retroviruses? How do they reproduce and what is the role of the enzyme reverse transcriptase?

Answer 1

Retroviruses are single stranded positive sense RNA virus , which are obligate parasite target a host cell.

Structure:-

The viruses consists of an outer envelope. The envelope is composed of lipids. Also there present glycoprotein.

Genome- the genome is diploid , composed of two identical single stranded v, positive sense RNA copies. In association with the viral RNA there present a enzyme called reverse transcriptase.

The genome is sorrounded by a nucleocapsid.

Reproduction-

It has enter a host cell before it gets multiplied.

In the host cell, the viral RNA is transcribed by the enzyme reverse transcriptase , first into single-stranded DNA and then to double-stranded DNA which integrates into the host cell chromosome. Here VIRAL RNA get transcribed into DNA.

The double stranded DNA is now called a pro viruses.

The provirus then with the help of host protein synthesis mechinary , makes viral nucleic acid and proteins.

Then viron assembly occurs in the host cell. At this stage only nucleocapsid is complete . Envelope are derived from host cell membrane during the process of budding.

So in this way New viruses are produced and viruses leave one host cell and infect other cell.