dna viruses : replication

dna viruses: replicATION :

three objectives :

1. to make their copy of dna genome

2. to make their proteins ( for this , they have to make m rna from dna and then , proteins from this m rna)

3. to do all this, they need enzymes present in the host...now these enzymes are present in nucleus of the host ..so, viruses have to enter the nucleus of the host ..

so, we have two types of viruses :

nuclear dna viruses :DNA replication occurs in the nucleus.

cytoplasmic dna viruses : POX VIRUS

NUCLEAR DNA VIRUSES :

1. PARVO :

Human parvovirus B-19 replicates in dividing cells – primarily in erythrocyte progenitors in the bone marrow - and causes fifth disease (erythema infectiosum). This is usually a mild disease but the decreased production of red blood cells can be a problem in people with various types of severe hemolytic anemia

2. papova viruses :

Papillomaviruses are difficult to grow in culture. and are a part of teh group DNA tumor viruses).

polyomaviruses :

Depending on the host cell, they can either transform the cell or replicate the virus and lyze the cell.