Quiz 3: Set I

Question 1

Picornavirus

Answer 1

+ssRNA
symmetry: icosahedral nucleocapsid

structure: hollow capsid w/ surface plateaus and canyons w/ CD155 receptor binding sites.

replication strategy: immediate translation of + strand. Proteases cleave products, incl. RNA replicase (transcribes genome), and kill CBP (necessary for host translation). Uses IRES for translation instead.

examples: enteroviruses (polio, coxsackie, echo, rhino), HAV.

Question 2

Reovirus

Answer 2

dsRNA (10 molecules)
symmetry: icosahedral nucleocapsid

structure: complex, frequent reassortments.

replication strategy: dsRNA makes mRNA using RDRP (essential polymerase) and vRNA that are part of virion (unlike polio) so genome isnt infectious (like picornavirus).

examples: rotavirus

Question 3

Orthymyxovirus

Answer 3

• ssRNA (8 molecules)
  symmetry: helical nucleocapsid

structure: enveloped, helical nucleocapsid surrounds each ssRNA segment

replication strategy: packaged with RDRP, HA and NA (cleaves off sialic acid for viral budding, infects cells of respiratory tract to cause influenza.

examples: influenza

[has RBC agglutination property]

Question 4

Paramyxovirus

Answer 4

• ssRNA (single)
  symmetry: helical

structure: enveloped, packaged with RDRP in virion; some have HA/NA.

replication strategy: don’t replicate RNA in nucleus (vs. influenza does).

examples: parainfluenza, RSV, measles, mumps.

Question 5

Coronavirus

Answer 5

+ssRNA (single)
symmetry: helical

structure: enveloped

replication strategy: n/a

examples: SARS, MERS, common cold.

Question 6

Hepadnavirus

Answer 6

(single) circular DNA, most of which is double-stranded
symmetry: icosahedral nucleocapsid

structure: enveloped

replication strategy: packaged with RT that fills in DNA gaps –> cellular RNA polymerase transcribes viral DNA. Late in infection, long pregenomes (RNA) are packaged in nucleocapsid, copied by RT into DNA while RNA is degraded, and virus buds through PM.

examples: Hep B

Question 7

Flavivirus

Answer 7

+ssRNA
symmetry: icosahedral nucleocapsid

structure: enveloped

replication strategy: 6 different genotypes.

example: Hep C

Question 8

Deltavirus

Answer 8

defective circular -RNA, only infectious w/ Hep B infection.

example: Hep D