Viruses

Question 1

Intracellular state

Answer 1

capsid removed, only nucleic acid

Question 2

Extracellular state

Answer 2

virion, capsid surrounding nucleic acid, phospholipid envelope

Question 3

What is the capsid

Answer 3

protein coat that protects nucleic acid

Question 4

What is nucleocapsid

Answer 4

capsid + nucleic acid

Question 5

5 classes of viruses

Answer 5

bacterial (bacteriophage), archaeal, animal, plant, other

Question 6

positive vs. negative polarity

Answer 6

positive same orientation as it mRNA, negative complementary orientation to mRNA

Question 7

3 shapes of viruses

Answer 7

helical, polyhedral, complex

Question 8

What is the capsomere

Answer 8

subunit of the capsid with same or diff types of proteins

Question 9

How is the length and diameter of viruses determined

Answer 9

Length: nucleic acid length

Diameter: width of capsomere

Question 10

What is the matrix protein

Answer 10

internal layer of envelope for extra protection

Question 11

What is the envelope composed of

Answer 11

acquired from host cell - phospholipid bilayer and proteins such as glycoproteins

Question 12

naked vs. enveloped virus

Answer 12

capsid + nucleic acid

envelope additional

Question 13

2 types of nucleocapsids

Answer 13

helical rod shaped viruses - length and width measurement

icosahedral spherical viruses - most efficient energetical arrangement of subunits

Question 14

Role of lysozyme in bacteria

Answer 14

makes hole in peptidoglycan in cell wall to lyse cell or allow nucleic acid to enter

Question 15

Role of neuroaminidase

Answer 15

cleave glycosidic bonds to allow liberation exocytosis of viruses

Question 16

Rate plant, bacteria, animal viruses in their efficiency to grow

Answer 16

bacterial, animal, plant

Question 17

What is confluency

Answer 17

% of surface covered by cells (higher = better)

Question 18

5 phases of viral replication

Answer 18

1. Attachment - virus attach to host cell
2. Entry - penetration of virion or nucleic acid
3. Synthesis - viral nucleic acid and protein made by cell metabolism (early and late phase proteins)
4. Assembly - capsids and viral genome packaged into mature virions
5. Release - virions leave cell

Question 19

What are early vs late stage proteins

Answer 19

Early: polymerase and genomic DNA (catalytic), smaller amount

Late: capsomere, assembly proteins, membrane viral rafts, larger amount

Question 20

3 mechanisms of viral entry

Answer 20

direct penetration, membrane fusion, endocytosis (double membrane bound)

Question 21

What makes up the latent phase

Answer 21

eclipse + maturation

Question 22

Why does viral load decrease when it first enters cell

Answer 22

Goes from extra to intra cellular state virus in cell as free nucleic acid not a virion

Question 23

How does bacteriophage T4 infect cells

Answer 23

virions attach cells via tail fibres, fibres retract and tail core lysozyme forms pores in peptidoglycan, viral DNA enters cytoplasm

Question 24

What are 2 ways that eukaryotic and prokaryotic cells prevent viral attack (2 each)

Answer 24

Immune defense, RNA interference

CRISPR, restriction modification enzyme systems (dsDNA viruses only) that cut viral DNA or modify host DNA to prevent cleavage and incorporation of viral DNA

Question 25

What are 2 ways that viruses evade our restriction modification system

Answer 25

chemical modifications on viral DNA, production of proteins that inhibit host system

Question 26

Name the 7 classes of Baltimore classification scheme

Answer 26

1. dsDNA 2. ssDNA 3. dsRNA 4. ssRNA (+) 5. ssRNA (-) 6. Retroviruses 7. dsDNA that replicate through RNA intermediate

Question 27

How does each class get to mRNA (+) 1. dsDNA 2. ssDNA 3. dsRNA 4. ssRNA (+) 5. ssRNA (-) 6. Retroviruses 7. dsDNA that replicate through RNA intermediate

Answer 27

1. DNA dependent RNA poly 2. replication to dsDNA intermediate then DNA dependent RNA poly 3. RNA dependent RNA poly 4. Used directly 5. RNA dependent RNA poly 6. RNA dependent DNA polymerase to dsDNA intermediate then DNA dependent RNA polymerase 7. DNA dependent RNA polymerase to ssRNA then RNA dependent DNA polymerase to dsDNA then DNA dependent RNA polymerase

Question 28

Where do DNA vs RNA viruses replicate

Answer 28

nucleus vs cytosol

Question 29

Which strand gets translated when making positive mRNA

Answer 29

antisense strand (negative strand)

Question 30

Lytic vs lysogenic cycle

Answer 30

Lytic: circular nucleic acid gets translated intro virions Lysogenic: circular nucleic acid gets integrated into host DNA via recombination

Question 31

What initiates lysogenic to lytic change

Answer 31

UV light, chemicals

Question 32

What is induction

Answer 32

viral nucleic acid excised from host genome to undergo lytic cycle

Question 33

What is prophage

Answer 33

host DNA and bacterial viral genome integrated together, translation repressed by 2 proteins encoded by phage genes

Question 34

difference between animal vs prokaryotic viruses

Answer 34

entire virion enters cell, not just the nucleic acid much more enveloped animal viruses

Question 35

4 consequences of viral infection in animal cells

Answer 35

1. persistent infection - release of virions does not lyse cell 2. latent infection - delay from infection and lytic events 3. transformation - normal cell to neoplastic tumour cell 4. cell fusion - cells become one with many nuclei (genomic stability of host genome)

Question 36

How do viruses leave the cell

Answer 36

budding - recognize viral glycoproteins (lipid rafts) and use host microtubule and microfilaments to bud

Question 37

What are retroviruses and what do they contain

Answer 37

2 copies of positive ssDNA integrated at 2 parts of the genome enveloped with a reverse transcriptase, integrase, and protease virion contains tRNA from host

Question 38

What genes do retroviruses have and what is the role

Answer 38

gag: structural proteins pol: reverse transcriptase and integrase env: envelope proteins

Question 39

What are 7 steps of retrovirus infection cycle

Answer 39

1. entrance 2. removal of envelope 3. reverse transcribe 1 of 2 RNA genome 4. integrate viral DNA into genome 5. transcribe viral DNA 6. assembly and packaging of genomic RNA 7. budding and release of virions