Ch.13 Viruses, Viroids, & Prions Part 1

Question 1

what do viruses infect?

Answer 1

infect host cells and exploit them to form new virions

Question 1

who is susceptible to virus infection?

Answer 1

cell types in all taxonomic domains

Question 2

who discovered viruses?

Answer 2

Ivanovsky and Beijernick

Question 3

what did Ivanovsky and Beijernick discover?

Answer 3

tobacco mosaic virus; “non-filterable particles”

Question 4

what is the size range of viruses?

Answer 4

20 to 90 nanometers

0.02 to 0.90 micrometers

Question 5

what are viruses defined as?

Answer 5

defined as acellular, obligate intracellular parasites

Question 6

define acellular

Answer 6

not consisting of cells

Question 7

defined obligate intracellular parasites

Answer 7

can reproduce/replicate only inside a host cell

Question 8

what do all viruses consist of?

Answer 8

nucleic acid (DNA/RNA) in a protein shell, a CAPSID
comprised of capsomere units

Question 9

what is the 1st step in the viral process?

Answer 9

Virus: host recognition

Question 10

what comes from the host of the virus?

Answer 10

DNA polymerase & RNA polymerase (dependent on virus type)
Ribosomes
tRNA’s
nucleotides

Question 11

what is the structure of capsids?

Answer 11

can vary in shape and size;
helical or polyhedral

Question 12

define genome structure:

Answer 12

single or double-stranded DNA or RNA

Question 13

describe enveloped viruses’ structure :

Answer 13

envelope surround capsid

Question 14

where is the envelope derived from?

Answer 14

host plasma membrane

Question 15

what do envelopes contain?

Answer 15

virus-specific proteins including glycoprotein spikes

Question 16

what is the function of glycoprotein spikes?

Answer 16

function in host recognition and attachment

Question 17

explain complex virus structure

Answer 17

have complicated structures; possess non-capsid protein components

ex: bacterial virus (bacteriophage)

Question 18

viral genomes need what?

Answer 18

very specific enzymes

Question 19

viral genes:

Answer 19

code for structural components, enzymes used in the life cycle ( viral genome replication/processing)

Question 20

small viruses of viral genome encode?

Answer 20

< ten genes

Question 21

larger viruses of viral genome encode?

Answer 21

> 100 genes

Question 22

what does the host range mean?

Answer 22

how many different hosts can the virus infect?

Question 23

what are the host ranges?

Answer 23

broad (infect many)
Ex: rabies virus

Narrow range(only infects some)
Ex:HIV infects only humans

Question 24

what does infectivity depend on?

Answer 24

virus: host recognition

interaction between viral surface proteins and host cell surface molecules

Question 25

what is tissue specificity?

Answer 25

infect certain types of cells or tissue within the host

Question 26

the genome of DNA virus:

Answer 26

can serve as a template for transcription

can serves as a template for DNA synthesis

Question 27

the genome of an RNA virus

Answer 27

can serve as a template for translation
—->(+) RNA viruses

can serve as a template for mRNA synthesis—> (-) RNA Viruses

can serve as a template for DNA synthesis —> retrovirus

Question 28

what is a viral species?

Answer 28

is a group of viruses sharing the same genetic information and host range

Question 29

the first step of viral infection

Answer 29

host recognition & attachment

via recognition/binding of the viral capsid, envelope proteins, or glycoprotein to host cell surface proteins/ glycoproteins

Question 30

the second step of viral infection

Answer 30

genome entry

the entire capsid + genome enters the host cell, or only the genome may enter

Question 31

the third step of viral infection

Answer 31

synthesis & virion assembly

genome replication, protein synthesis; assembly of virions

Question 32

the 4th step of viral infection

Answer 32

release from host cell—> progeny infect more host cells

Question 33

how are viral species classified?

Answer 33

classified based on genome type and the presence or lack of an envelope

Question 34

what is virions?

Answer 34

complex viral particle