C-5

Question 1

capsid

Answer 1

protein coat around virus

Question 2

nucleocapsid

Answer 2

capsid and nuclei acid

Question 3

genome

Answer 3

made of RNA and DNA

Question 4

envelope

Answer 4

a phospholipid membrane that surrounds the capsid and acquired from host cell

Question 5

steps of lytic vs lysogenic bacteriophage replication cycles

Answer 5

lytic- fills cells with viruses until it explodes so virus gets out

lysogenic- inserts own DNA into host’s DNA and stays with the cell even as it divides instead of injecting and leaving

Question 6

what is lysogenic conversion and why is it important in the evolution of human pathogens

Answer 6

when the integrated virus gives the host new abilities and characteristics; it stays with the cell as it divides creating these new changes

Question 7

steps of animal virus replication cycles

Answer 7

1. attach to host cell
2. enter host cell
3. replicate genetic material and make protein
4. assemble new genetic material and proteins together
5. leave the cell and find a new one

Question 8

how are viral genomes replicated

Answer 8

1. replicate the genome you came into the cell with
2. make mRNA that the host cell’s ribosomes can recognize and translate into protein

Question 9

how are mRNAs produced to make protein capsids from host ribosomes

Answer 9

gene expression

Question 10

how replication occurs for (+)ssRNA

Answer 10

reverse transcriptase

Question 11

how replication occurs for (-) ssRNA

Answer 11

RNA-dependent RNA transcriptase

Question 12

how replication occurs for ssDNA

Answer 12

RNA polymerase in nucleus

Question 13

how replication occurs for dsRNA

Answer 13

positive strand of genome acts as mRNA

Question 14

how replication occurs for dsDNA

Answer 14

cellular RNA polymerase in nucleus or viral RNA polymerase in cytoplasm

Question 15

how replication occurs for retroviruses

Answer 15

reverse transcriptase; back in molecular time

Question 16

What is meant by “positive sense” and “negative sense” single-stranded RNA?

Answer 16

negative sense: starts 3’-5’

positive sense: starts 5’-3’

Question 17

how do enveloped viruses enter and exist cells

Answer 17

membrane fusion (membrane encloses around virus); endocytosis

budding (steals host cell’s plasma membrane for its own envelope; takes membrane with); lysis

Question 18

how do naked viruses enter and exist cells

Answer 18

direct penetration (capsid empties its genome into host cel); endocytosis

exocytosis or lysis

Question 19

how do bacteriophages enter and exit cells

Answer 19

inject DNA into cytoplasm of bacterial cell

the mature virions lyse the cell, are released, and go to infect a new cell

Question 20

what enzymes are involved in replicating each type of virus based on its genome

Question 21

which enzymes are provided by the host cell and which are produced exclusively by the virus

Answer 21

provided: DNA polymerase, RNA polymerase, ribosome

produced: RNA replicase, reverse transcriptase

Question 22

lysogenic viral infections

Answer 22

stays with cell as it continues to divide

Question 23

lytic viral infections

Answer 23

sometimes the host cell is killed in the process

Question 24

latent viral infections

Answer 24

sometimes the host cell survives but the virus remains in the cell

Question 25

what are adhesions? what step of replication are they necessary for?

Answer 25

attach step; all viruses to bind to new receptors

Question 26

Describe how we treat and prevent viral infections

Answer 26

- antiviral drugs - broad-spectrum strategies - vaccines

Question 27

what are nucleoside analogs and reverse transcriptase inhibitors

Answer 27

generic viral enzymes; virus specific enzymes

Question 28

how do antiviral drugs like these (nucleoside analogs and reverse transcriptase inhibitors) work? Why can’t we use antibiotics to treat viral infections?

Answer 28

target host cell functions; viruses don't have cell walls that can be attacked by antibiotics

Question 29

how can viruses cause uncontrolled cell growth and cancer

Answer 29

1. produce a protein that inhibits cell division regulators 2. integrate into host DNA and into genes that regulate cell division

Question 30

cytopathic effects on viral infection

Answer 30

observable morphological changes in host cells that occur because of viral infections

Question 31

plaques

Answer 31

produced by lytic HSV from lysed VERO cells in tissue culture

Question 32

syncytia

Answer 32

formed by RSV; when the virus fuse host cells together to form one multi-nucleated mega cell

Question 33

inclusion bodies

Answer 33

clumps of viral capsid proteins inside the cytoplasm of the host cells

Question 34

Describe the methods used to culture viruses (4)

Answer 34

primary; harvested directly from tissue continuous: derived from cancer cells embryonated: can grow higher quantities of viruses - used to produce viruses (chicken eggs) animal models: infect animals with virus

Question 35

viruses

Answer 35

nucleic acid and protein

Question 36

viroids

Answer 36

pieces of ssRNA that lack capsids and do not code for proteins (only RNA); replicates using host cell RNA polymerase

Question 37

prions

Answer 37

only made of protein