week 1

Question 1

capsid

Answer 1

protective protein shell surronding the genome and forming the core of the viral particle. clusters of capsid protein subunits are called capsomers

Question 2

nucleocapsid

Answer 2

made up of the proteins most closely assembles with the viral nucleic acid. sometimes this is the capsid proteins if these form a substructure of the virion (if they have an envelope) or it can be proteins associated with the genome

Question 3

envelope

Answer 3

lipoprotein membrane surronding either nucleocapsid or capsid. the phospholipids are derived from the host cell membrane and the glycoproteins are virus encoded. naked viruses lack an envelope

Question 4

matrix

Answer 4

some viruses have a protein layer beneth the envelope that connects the capsid and envelope glycoproteins

Question 5

structure of all (-)ssRNA viruses

Answer 5

helical and enveloped

Question 6

the (+)ssRNA viruses structure is generally…

Answer 6

icosahedral, either naked or enveloped.

Question 7

how to detect viruses

Answer 7

• viruses can be visualized directly by EM.
• can also cultivate them which is the gold standard for the study of viruses. takes time and some viruses are not possible to cultivate. cultivation and the information that comes from it usually ahs no impact on treatment.
• viral protein (antigen) detection. can use flouroscent markers
• haemgglutination assay: measures the ability of virus particles to aggregate red blood cells (takes a certain amount of particles to do this). serial dilutions of virus are mixed with a constant amount of red blood cells
• western blot: proteins from infected cells are separated by SDS PAGE and transferred to filters. anti-viral antibody in patients serum binds to the protein bands.
• detect viral DNA by southern blot and RNA by northern blot
• PCR for DNA and reverse-transcriptase PCR for RNA

Question 8

purify virus from host cell

Answer 8

• freeze and thaw to disrupt cell
• use detergent to lyse cytoplasmic but not nuclear membrane, works if the virus is in the cytoplasm
• rapidly rotation blades: nuclei are broken releasing DNA and chromatin

Question 9

analysis of virus components step by step

Answer 9

• ultracentrifugation
• centrifugation: after high speed thhe virus partivles should be in the pellet. can then be resuspended and centrifuged again
  density gradient centrifugation: rate zonal density gradient centrifugation separates depending on sedementation coeffecient meaning both size and mass. equilibrium centrifugation separates on density only, takes a long time

Question 10

how to determine whether virus is DNA or RNA virus?

Answer 10

infect cells in the presence of radiactively labelled thymidine and uracil. purify the virus particles produced in the cells and use a radiactivity detector to determine if cells contain uracil (meaning its an RNA virus) or thymidine

Question 11

does it contain ssRNA or dsRNA?

Answer 11

label viral RNA during growth and extract nucleic acid from purified particles, divide into two portions. add a ribonuclease to one and incubate, RNase digests ssRNA but not dsRNA