viruses

Viruses

-Virus : obligate intracellular parasites .

-Virus contain two genomes DNA or RNA But not both .

which contain :- ss : single stranded . ds : double stranded

-Capsid :- protein shell that enclose the viral genome .

-Capsid symmetry : (( cabic – helical – complex ))

-Viral Enveloped : help in infect host and composed of lipid bilayer and glycoprotein

-Bacterophage :- viruses that infect bacteria cell ( prokaryotic )

-Virion :- complete virus particle : nuclic acid + protein . it is extracellular phase of

virus (( before virus enter host cell ))

-Vector virus passed from host to host through direct contact and vector .

-Nucleocapsid :- viral nucleic acid + protein coat .

-Viroids : is naked circular single strand RNA that infect plants . it is the smallest

known pathogens .

-Prions :- is infectious proteins cause brain disease e.g :- mad cow and CJD in

human .

-DNA viruses replicate in nucleus of host except " poxvirus "

-RNA viruses replicate in cytoplasm except " influenza & retrovirus "

-most plants viruses are RNA viruses .

-Virus may be :- monomorphic , dimorphic , pleomorphic .

-Reproductive in virus :- by assembly of individual components .

-

-Viral Replication Steps :-

 Recognition of target cell .

2- Attachment

3- penetration :- By Endocytosis .

4- uncoating

5- replication

6- assembly

7- budding

8- release

DNA viruses :-

1-Poxviridae

2-herpesvirdiae

3-adenovirdiae

4-hepadnavirdiae

5-papilomavirdiae

6-parvovirdiae

7-polyomvirdiae