Question

Drugs against viruses are usually designed to affect viral genome replication.

i) Describe the various mechanisms by which viral genomes replicate and also synthesize protein. Your answer needs to focus only on genome replication and protein synthesis; do not include the other replication steps.

Answer 1

The viral genome replication involves the following steps:

1. Attachment and adsorption : the viral body consists of envelop, capsid and genome. The envelop is made up of glycoproteins which binds to the specific receptor on the host cell membrane to enter inside the host.

2. Penetration: When virus fuses to the host cell receptor which penetrated the capsid and genome in the host.

3.Uncoating: Removal of the capsid. The digestive enzymes present in the host cells dissolve the capsid.

4.Early Viral m-RNA synthesis: the transcription begins. RNA virus replicates in cytoplasm while DNA in nucleus. The virus has its own synthesised enzymes to replicate. Therefore, drugs are designed accordingly.

There are two types of replication cycle: LYTIC and LYSOGENIC

In lytic cycle: lytic means breaking up. the viral genome DNA breaks the host cell by destroying the cell DNA. Then virus replicates and progenies are formed. The replication is fast.

In lysogenic cycle the virus does not destroy the host cells to replicate. The virus DNA incorporate with host DNA. Then cells replicate normally. Here, The DNA remains dormant and activates and switches into lytic cycle after some years or a period of time. It is transfered to future generation.

5. Viral protein synthesis: The host cell ribosomes are required to produce the viral protein. The translation process is same as that of host.