Unit 1--Lecture 6 (Virus Structure and Function)

Question 1

Virus

Answer 1

Not a living cell

Has small genome

Always has a protein coat
-capsid

Question 2

Scale of Viruses

Answer 2

20 to 200 nm

Question 3

Virus Structure–Capsids

Answer 3

Icosahedral capsids
-20 triangular sides

Filamentous (helical) capsids
-long tube of protein, with genome inside

Complex capsids
-mixture of icosahedral and filamentous shapes

Question 4

Virus Structure–Envelopes

Answer 4

Lipid envelope

Envelope lipids come from host

Bacteriophages are non-enveloped

Question 5

Virus Structure–Genome

Answer 5

DNA or RNA

SS or DS

Linear or circular

Question 6

Viral Genomes and Classification–Group I

Answer 6

dsDNA (Poxvirus)

Question 7

Viral Genomes and Classification–Group II

Answer 7

ssDNA (Parvovirus)

Question 8

Viral Genomes and Classification–Group III

Answer 8

dsRNA (Epizootic Hemorrhagic Disease)

Question 9

Viral Genomes and Classification–Group IV

Answer 9

(+)ssRNA (Poliovirus)

coding strand

Question 10

Viral Genomes and Classification–Group V

Answer 10

(-)ssRNA (Influenza virus)

Question 11

Viral Genomes and Classification–Group VI

Answer 11

RNA retroviruses (HIV)

Question 12

Viral Genomes and Classification–Group VII

Answer 12

DNA pararetroviruses (Hepatitis B)

Question 13

Viral Life Cycles

Answer 13

1. Attach to host cell
2. Get viral genome into host cell
3. Replicate genome
4. Make viral proteins
5. Assemble capsids
6. Release progeny viruses from host cell

Question 14

Bacteriophage Life Cycles

Answer 14

1. Attach to host cell receptor proteins
2. Inject genome through cell wall to cytoplasm
3. Replicate genome
4. Synthesize capsid proteins
5. Assemble progeny phase
6. Lyse cell wall to release progeny phage

Question 15

Hershey-Chase Experiment

Answer 15

Protein labeled with S Methionine

DNA labeled with P Phosphate

Infected E. Cole

P entered cells during infection, not S (DNA not protein)

Question 16

Lytic Cycle

Answer 16

Phage quickly replicates, kills host cell

Question 17

Lysogenic Cycle

Answer 17

Phage is quiescent
-may integrate into host cell genome
-replicates only when host genome divides

Question 18

Eukaryotic Virus Life Cycles

Answer 18

Entry into cell
-taken up via endocytosis (viropexis)

Genome replication
-DNA viruses must go to cell nucleus

-RNA viruses must encode a viral polymerase
–only (+)ssRNA can be used as mRNA

All viruses make proteins with host ribosomes

Budding
-all enveloped viruses bud to form envelope

Question 19

Culturing Viruses

Answer 19

Viruses bound to host

Eclipse period

Rapid rise period

Question 20

Culturing Viruses on Plates

Answer 20

Plaque is a colony of viruses

Question 21

Viral Ecology

Answer 21

Viruses present in all environments
-often at very high densities

Question 22

Viroids

Answer 22

Naked RNA

Question 23

Prions

Answer 23

Defectively folded host protein

Mad Cow Disease

Creutzfeldt-Jakob disease