Viral structure and Replication?

Question

i.What is the structure of viruses?
ii.What are the major steps in viral reproduction?
iii.How do viruses transfer genetic material between cells?

Answer 1

1. Viruses come in five different kinds of structures:

Icosehedral
Spherical
Rod shaped (either hard rods or filamentous rods)
Bacilliform (bullet shaped)
Tailed phages (the traditional picture most people have of viruses)

2. The steps of viral reproduction vary greatly depending on the type of virus and what form of nucleic acid they have. For example, DNA viruses replicate much like their host DNA, in the nucleus. RNA viruses replicate in the cytoplasm, by making a copy of their RNA, then using that copy as a template to make many copies of the encapsidated strand. Retroviruses make a DNA copy of their RNA, which is shipped to the nucleus and inserted into the host chromosome. This DNA acts as a template for replicating more RNA.

At any rate, after nucleic acid replication the nucleic acid is encapsidated in protein to form virions.

3. Some viruses insert copies of their DNA into their host DNA. If this DNA conains genetic information from a previous host, gene transfer occurs. In reality, very few if any viruses actually transfer genetic material between cells. This is mostly done by transposable elements.

Answer 2

as an appendix to the above answer, virally infected cells do not always burst: Some of them just release virus particles periodically eg HIV. You can usually tell which ones these are because they have a membrane surrounding them - Poilio for example causes a cell to lyse (break open) and it has no membrane.

Answer 3

I type htis up somewhere.....

There are four types of stuctures for a virus

Icosahedral (isometric) capsids
Helical capsids
Enveloped viruses
Tailed Phages


They transmite their genetic material between cells by invadeing one cell, and altering it to jsut produce more viral DNA. After time the cell expolodes and the viral DNA attacks other invading cells....chaos..lol

Sry i dunno the steps

But htis site will help you alot

http://www-micro.msb.le.ac.uk/109/structure.html