Virus facts

Question 1

Polyomaviruses structure

Answer 1

Non-enveloped spherical virions with 4- to 5-kbp circular dsDNA genome

Question 2

HPV structure

Answer 2

Spherical virions with circular dsDNA genome 6-8.5kbp

Question 3

Poxviruses structure

Answer 3

• Largest dsDNA virus that infect humans
• Linear genome is composed of 194 kbp of dsDNA with inverted terminal repeats that form covalently closed hairpin termini
• Enveloped, brick-shaped or ovoid virion

Question 4

Flaviviruses structure

Answer 4

• Enveloped, spherical virions, 10-12kb, +ssRNA genomes
• 5’ cap similar to host mRNA
• Lack 3’ poly A tail, instead 3’ UTR folds into secondary structures with several stem loops

Question 5

Picornaviruses

Answer 5

lack 5’ cap and itilise VPg protein and IRES

Question 6

Baltimore class V

Answer 6

-ssRNA that may be segmented or non segmented

Question 7

Mononegavirales

Answer 7

• ss(-)RNA viruses with non segmented genomes
• Replicase / transcriptase

Question 8

Orthomyxoviridae

Answer 8

• Influenza
• 8 genome segment sbeach bound to NP and PA, PB1 and PB2

Question 9

Reoviridae / rotavirus

Answer 9

• Non enveloped, icosahedral virion with triple capsid structure
• Segmented linear dsRNA genome with 11 segments coding for 12 proteins
• Each segment has 5’ cap, no polyA tail

Question 10

Rotavirus site of viral dsRNA synthesis

Answer 10

Viroplasm

Question 11

Rotavirus site of early transcription of dsRNA genoma by RdRp

Answer 11

Inside double layered particle

Question 12

HIV part 1

Answer 12

• HIV-1 infects CD4+ T cells via binding of surface gp120 to CD4 receptor
• This triggers a conformational change that initiates gp120 binding to a co-receptor CCR5/CXCR4
• This triggers rearrangement of the gp120-gp41 complex such that the fusion peptide of gp41 inserts into the plasma membrane and the two fuse.
• The HIV nucleocapsid releases into the cytoplasm, releasing the viral RNA genome and enzymes (RT, integrase, protease) into the cytoplasm
• RT converts ssRNA into dsDNA which is transported into the nucleus where it integrates into a host chromosome using viral integrase

Question 13

HIV part 2

Answer 13

• Viral genes are transcribed by host pol II to produce eukaryotic mRNA and mRNA is transported to cytoplasm where translation occurs
• Some proteins enter the nucleus to affect gene expression
• Major structural proteins that form the internal parts of the virion are synthesised as polyproteins Gag, Gag-pol and Env.
• Protease cleaves Gag/Gag-pol polyproteins to produce infectious virus particles with a morphologically distinct core
• HIV-1 nef/vpu mediate translocation of cell-surface CD4 to the cytoplasm/lysosol allowing new virions to leave the cell