6 - Diversity of viruses and viral replication

What is the range for virion sizes?

0.2-0.5um

What are all the structural diversity of viral genomes?

ssDNA or dsDNA / ssRNA or dsRNA / Both DNA & RNA depending on stage

What genome does retroviruses have?

RNA genome, replicate via DNA intermediate + reverse transcriptase

What genome does hepadnaviruses have?

DNA genome, replicate via RNA intermediate

State, the extracellular state of a virion.

Nucleic acid / capsid / may be enveloped / metabolically inert

What is a capsid?

Polymer of a single protein or several proteins

What are the different structures of capsids?

Icosahedral / helical

What is the membrane surrounding the capsid of a virus called?

envelope

Are all viruses enveloped?

No, can either be enveloped or naked

What is an envelope?

Host membrane +/- virus specific protein

What are some examples of naked viruses?

TMV / polio virus

What is the structural / genome description of TMV?

Helical / naked / ssRNA

What is the structural / genome description of polio virus?

Icosahedral / naked / ssRNA

What are some examples of envelopes viruses?

Herpes / coronavirus / paramyxoviruses

What does the viral envelope of influenza contain?

Haemagglutinin H, 15 types / neuraminidase N, 9 type ‘spike’ e.g. H5N1

What happens as soon as a virus enters a host cell?

Capsid break down, genome is released

What is the process of virus replication cycle? (6 steps)

1. Attachment to receptor

2. penetration

3. uncoating / expose nucleic acid

4. synthesis of nucleic acid and proteins

5. assembly of structural subunits + packaging of genome

6. release of mature virions

What is happening at the ‘eclipse’ on a one step growth curve?

Coat & nucleic acid separated

What is happening at the ‘latent period’ on a one step growth curve?

Replication & protein synthesis begins / virions start to assemble & accumulate

What is happening at the ‘Rise period’ on a one step growth curve?

Viruses assemble / extracellular viruses detected

State the history of the ‘one step growth curve’.

Ellis and Debruck / 1939

What is the ‘burst size’?

Number of virion released from a single cell

What is the process called, when a virus enters a cell?

Endocytosis

What is the process called, when a virus exits a cell?

Budding

What are all the components in a bacteriophage?

Icosahedral heads / helical tail sheath / helical tail fibers