Viruses

Question 1

what does obligate mean?

Answer 1

relies on the host cell for life

Question 2

what does the host cell provide for the virus?

Answer 2

nucleotides, ribosomes and amino acids, ATP and Golgi and the ER

Question 3

what do viruses use the provided nucleotides for?

Answer 3

nucleic acid production

Question 4

what do viruses use the provided golgi and ER for?

Answer 4

protein processing

Question 5

what are the catagories of viruses?

Answer 5

nucleic acid either RNA/DNA, capsid symmetry, presence of envelope and the genome characteristics

Question 6

what are the different structures of capsid symmetry?

Answer 6

helical, icosahedral or complex

Question 7

what are the main viral characteristics?

Answer 7

nucleic acid, protein coat, maybe an envelope or capsule

Question 8

what is a nucleocapsid?

Answer 8

the capsid and the nucleic acid

Question 9

what are capsomers?

Answer 9

the proteins that make up the capsid, they form the capsid spontaneously

Question 10

what shapes can the capsid have?

Answer 10

polyhedral or helical

Question 11

what is the arrangement of a nucleocapsid?

Answer 11

highly symmetrical, composed of one protein and capsid is formed via self-assembly by capsomeres

Question 12

what is a bacteriophage?

Answer 12

viruses that infect and replicate within bacteria

Question 13

why are bacteriophages bad for bacteria?

Answer 13

highly virulent

Question 14

what is a bacteriophage classified by?

Answer 14

nucleic acid type and shape

Question 15

what are the physical features of a bacteriophage?

Answer 15

head, collar, tail and tail pins, tail fibres

Question 16

how many steps in a bacteriophage life cycle? what are they?

Answer 16

5; attachment, penetration, synthesis of nucleic acid, assembly, lysis

Question 17

how are bacteriophages specific?

Answer 17

infect one species only

Question 18

how do bacteriophages attach to host cells?

Answer 18

viruses have attachment proteins on their surface which attaches to specific receptors on the host cell surface

Question 19

what are the receptors that the virus attaches too?

Answer 19

essential proteins on the surface of the host cell

Question 20

what are two examples of bacteriophages?

Answer 20

T4 and lambda

Question 21

what is different about the structure of lambda?

Answer 21

no tail pins or tail fibres

Question 22

what is the difference between lambda and T4?

Answer 22

lambda is temperate yet T4 is virulent

Question 23

what are the two life cycles of lambda?

Answer 23

lytic and lysogenic

Question 24

what is the lytic cycle?

Answer 24

bacteria genome is destroyed and the cell becomes a factory for making bacteriophages

Question 25

what is the lysogenic cycle?

Answer 25

DNA of the virus gets inserted into the bacterial genome so it becomes a prophage, which is passed on to future generations

Question 26

how can a lysogenic cycle turn into a lytic cycle?

Answer 26

a prophage exits the bacterial chromosome

Question 27

what is the only function of T4?

Answer 27

the lytic cycle

Question 28

how is phage DNA inserted into bacterial genome?

Answer 28

via genetic recombination which occurs at a specific point on the genome

Question 29

what occurs in assembly and packaging of bacteriophages?

Answer 29

stage of maturation where the viral components are assembled into virions

Question 30

what is an example of a plant virus?

Answer 30

tobacco mosaic virus

Question 31

what are the features of tobacco virus?

Answer 31

helical symmetry, 2130 identical capsomers, helical nucleocapsid

Question 32

what kind of nucleic acid does the tobacco virus have?

Answer 32

RNA

Question 33

how do plant viruses enter a cell?

Answer 33

endocytosis

Question 34

how does the tobacco virus spread across the leaf?

Answer 34

infects all cells as they are connected together

Question 35

what kind of virus is the most varied?

Answer 35

animal viruses

Question 36

what is a key structure of an animal virus?

Answer 36

they have an envelope

Question 37

what is an example of a non-enveloped virus?

Answer 37

picornavirus

Question 38

what does picornavirus look like?

Answer 38

icosahedral virus without an envelope

Question 39

where does the envelope come from?

Answer 39

either the cell, golgi or nuclear membrane

Question 40

how do enveloped viruses escape from a cell?

Answer 40

via budding or bursting

Question 41

what are some examples of enveloped viruses?

Answer 41

measles, influenza

Question 42

what are matrix proteins?

Answer 42

they connect the nucleocapsid to the membrane

Question 43

how are the surface glycoproteins useful?

Answer 43

act as main antigens for immune system

Question 44

what are the two glycoproteins of influenza?

Answer 44

H-haemaglutanin and N-neuraminidase

Question 45

what makes it difficult for the immune system to recognise influenza?

Answer 45

they can change their surface proteins visa antigenic shift

Question 46

what are the methods of entry of a virus?

Answer 46

direct penetration, membrane fusion and endocytosis

Question 47

how do naked viruses enter?

Answer 47

direct penetration

Question 48

how do enveloped viruses enter?

Answer 48

membrane fusion

Question 49

what does the ER of the cell do in an enveloped virus life cycle?

Answer 49

makes viral glycoproteins

Question 50

where in the cell is enveloped virus assembly taken place?

Answer 50

the golgi, nuclear or cell membrane

Question 51

does an enveloped virus life cycle kill the cell initially?

Answer 51

no, the cell only dies once it runs out of resources

Question 52

how do the assembled enveloped virus escape from the cell?

Answer 52

endocytosis

Question 53

what is HIV?

Answer 53

ss enveloped RNA virus

Question 54

what is a retrovirus?

Answer 54

the RNA of the virus gets converted into DNA via retrotranscriptase

Question 55

how is the HIV viral DNA incorporated into host DNA?

Answer 55

imported into the nucleus

Question 56

can HIV become latent? what does this mean?

Answer 56

yes, which means it can lie dormant within the cell

Question 57

what are the effects of viruses on cells?

Answer 57

cytopathic effects, transformation into tumour cell, lysis, persistent infection, latent infection

Question 58

what is persistent infection?

Answer 58

slow release of the virus without cell death

Question 59

what happens in latent infection of a cell?

Answer 59

virus is present but not causing harm, later emerges in lytic infection

Question 60

how do you grow viruses in culture?

Answer 60

provide with specific types of cells so you can analyse their effects

Question 61

what is primary cell culture? why is it listed?

Answer 61

cells obtained from animal tissue yet limited life of the tissue

Question 62

what is diploid cell lines? why is use limited?

Answer 62

homogenous cells from embryos, yet divide about 100 times and then they die

Question 63

what is continuous cell lines?

Answer 63

use cancerous cells to produce an immortal cell line that does not stop growing

Question 64

how do you count viruses?

Answer 64

plaque assay

Question 65

what is a plaque assay?

Answer 65

virus innoculated on a single monolayer and an overlay of agar is added, causing plaques of the dead cells to form in the monolayer