Virus Infection and Replication

+(ss)RNA tricks host cells into thinking it is mRNA

Binds to ribosomes

translation and viral protein synthesis

-(ss)RNA cannot bind to host ribosomes

Using packaged polymerase, transcribes to +(ss)RNA

How positive sense and negative sense viral RNA works

RNA dependent RNA polymerase

General Phases of Animal Virus Multiplication Cycle

Adsorption (attachment)

Penetration (entry)

Uncoating

Synthesis

Assembly

Release

binding of virus to specific molecule on host cell -- may require viral spirke

genome enters host cell (different for envelop vs. nake virus)

the viral nucleic acid is released from the capsid

viral production of proteins (structural and enzymatic) and replication of genome

new viral particles are constructed & synthesis of nucleocapsid

viruses are released by budding (exocytosis) or cell lysis

Synthesis of DNA Virus

dsDNA

dsDNA

copy

DNA-dependent DNA polymerase

copies both + & - DNA strands

viral genome

mRNA

(+ssRNA)

DNA dependent RNA polymerase

transcription

viral proteins

(structural - capsid)

(functional - enzymes)

Translation

Assembly

viral protein

ssDNA

produces complementary DNA strand and forms dsDNA

Synthesis of +(ss)RNA Virus

+(ss)RNA

Virus

viral proteins

& polypeptides

translation acts as mRNA

transcription by RNA dependent RNA polymerase

-(ss)RNA

copies of +(ss)RNA (genome)

transcription

viral protein

assembly

Synthesis of -(ss)RNA Virus

viral protein

viral proteins

& polypeptides

-(ss)RNA Virus

+(ss)RNA

translation

transcription by RNA depdendent RNA Polymerase

copies

-(ss)RNA

transcription

assembly

Synthesis of (ds)RNA Virus

+(ss)RNA

viral proteins

translation

-(ss)RNA

transcription by viral RNA polymerase

complementary strands

viral protein

assembly

(ds)RNA virus

unwinding