Viruses

What is a virus? ‘Infectious particle’ Genetic material Protein coat

Properties of a virus A virus is a very small, infectious, obligate intracellular parasite Virus particles are not living Viruses are chemicals, and by themselves cannot reproduce A susceptible and permissive cellular host is needed for viruses to reproduce All viruses must make mRNA that can be translated by host ribosomes

Basic virus structure

Basic virus structure DNA DNA OR OR RNA RNA

Basic virus structure DNA RNA OR DNA + + OR RNA

Basic virus structure + + DNA RNA OR DNA Capsid Protein Capsid Protein

Basic virus structure + + DNA RNA OR DNA Capsid Protein Capsid Protein

Basic virus structure DNA RNA OR + Capsid Protein Nucleocapsid

Basic virus structure DNA RNA + Capsid Protein Nucleocapsid OR

Basic virus structure DNA RNA OR + Capsid Protein Nucleocapsid =

Basic virus structure DNA RNA OR + Capsid Protein Nucleocapsid = +

Basic virus structure + + = DNA Capsid OR Protein RNA Nucleocapsid Lipid membrane + Glycoproteins

Basic virus structure + + = Enveloped virus DNA Capsid OR Protein RNA Nucleocapsid = + Lipid membrane Glycoproteins Enveloped virus

Capsid symmetry Icosahedral Helical

Attachment

Attachment: tropism Lock and key

Penetration

Disassembly

Disassembly Viral genome

Transcription Viral genome Viral enzymes mRNA

Translation Viral genome Viral enzymes mRNA Viral proteins

Genome replication Viral genome mRNA Viral proteins

Assembly mRNA Viral proteins

Assembly Viral genome mRNA Viral proteins

Release

Retroviruses

Outcome of cellular infection

Immune response Cell mediated immunity Antibodies Important in the recovery from viral illness Antibodies Important in the protection from repeat exposure