Chapter 19

Question 1

virus

Answer 1

an infectious particle consisting of genes packaged in a protein coat

Question 2

Can viruses reproduce or carry out metabolism outside of a host cell?

Answer 2

No

Question 3

What 2 macromolcules make up viruses?

Answer 3

nucleic acid and protein (sometimes membrane envelope)

Question 4

tobacco mosaic virus

Answer 4

first studied virus (crystallized)

Question 5

Types of viral genomes

Answer 5

DNA or RNA

Question 6

What shape is the genome of a virus?

Answer 6

linear or circular

Question 7

What is the fewest number of genes a virus can have?

Answer 7

3

Question 8

capsid

Answer 8

protein shell that encloses the viral genome

Question 9

capsomeres

Answer 9

protein subunits that make up capsids

Question 10

bacteriophages

Answer 10

viruses that infect bacteria (most complex capsids)

capsid head and protein tail (injects DNA inside)

Question 11

viral envelopes

Answer 11

surround the capsids of influenza viruses and many other viruses in animals (derived from membranes of host cells)

Question 12

obligate intracellular parasites

Answer 12

can replicate only within a host cell

Question 13

host range

Answer 13

a limited number of host cells that it can infect

Question 14

What happens when a viral genome enters a cell?

Answer 14

The cell begins to manufacture viral proteins

Question 15

How do viral nucleic acid and capsomeres become new viruses?

Answer 15

spontaneous self-assembly

Question 16

2 reproductive mechanisms of phages

Answer 16

the lytic cycle

the lysogenic cycle

Question 17

lytic cycle

Answer 17

phage replicative cycle that culminates in the death of the host cell through the lyses of the cell wall

Question 18

virulent phage

Answer 18

only uses lytic cycle to reproduce

Question 19

restriction enzymes

Answer 19

part of bacteria, attack phage DNA

Question 20

lysogenic cycle

Answer 20

replicates phages without destroying host

incorporates viral DNA into cell’s chromosome and then it is copied when the cell divides

Question 21

prophage

Answer 21

integrated viral DNA

Question 22

Can a virus switch from lysogenic to lytic? How?

Answer 22

Yes; environmental changes

Question 23

temperate phages

Answer 23

used lysogenic and lytic cycles

Question 24

2 variables used to classify viruses that infect animals

Answer 24

an RNA or DNA genome

a single-stranded or double-stranded genome

(many have additional envelope)

Question 25

What binds to specific receptor molecules on the surface of a host cell?

Answer 25

viral glycoproteins on the envelope of the virus

Question 26

What is used to form the viral envelope?

Answer 26

The host cell's plasma membrane or the host's nuclear envelope and then Golgi apparatus

Question 27

retroviruses

Answer 27

use reverse transcriptase to copy their RNA genome into DNA

Question 28

HIV (human immunodeficiency virus)

Answer 28

the retrovirus that causes AIDS (acquired immunodeficiency syndrome)

Question 29

provirus

Answer 29

the viral DNA that is integrated into the host genome makes proviral DNA into RNA for mRNA and as genomes released from the cell

Question 30

How long is a provirus part of the host?

Answer 30

Always

Question 31

How may viruses damage or kill cells?

Answer 31

by causing the release of hydrolytic enzymes from lysosomes cause infected cell to produce toxins toxic envelope protein

Question 32

Vaccines

Answer 32

harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the harmful pathogen

Question 33

emerging viruses

Answer 33

those that suddenly become apparent

Question 34

pandemics

Answer 34

global epidemics

Question 35

What is true of most plant viruses?

Answer 35

RNA genome helical or icosahedral capsid

Question 36

Mode of plant virus spread

Answer 36

horizontal transmission (enter through damaged cell walls) vertical transmission (inheriting the virus from a parent)

Question 37

viroids

Answer 37

small circular RNA molecules that infect plants and disrupt their growth

Question 38

prions

Answer 38

slow-acting, virtually indestructible infectious proteins that cause brain diseases in mammals (convert normal proteins into prion version)