taxonomy - viruses

Question 1

viruses are group into families that end in —-

Answer 1

viridea

Question 2

viruses are given a genus name that end in —

Answer 2

virus

Question 3

viruses are given a species name usually in —

Answer 3

English

Question 4

classification is based on: 
1)
2)
3)
4) 
5)

Answer 4

1) nature of the host –> animal, plant, etc
2) type of disease caused –> e.g. centric, leukaemia, pneumonia
3) life cycle
4) naked or enveloped
5) type of nucleic acids and strandedness

Question 5

life cycle depends on the —-

Answer 5

genome

Question 6

the Baltimore classification scheme is based on:

why is it useful?

Answer 6

the type of genome

it is useful because the type of genome will dictate the replication mechanism

Question 7

name the 2 configurations of the RNA genome

Answer 7

plus configuration and minus configuration

Question 8

adsorption

Answer 8

attachment of the virus to specific receptors on the surface of the cell

Question 9

plant viruses are usually introduced onto the host by ——-, or following ——

Answer 9

insect vectors, mechanical damage

Question 10

penetration

Answer 10

virus genome enter the cell

Question 11

—- and —– viruses , the complete vision may enter the cell

Answer 11

enveloped , naked

Question 12

in —- viruses, the envelope may be left outside the cell such that only the —- may enter

Answer 12

enveloped, nucleocapsid

Question 13

in naked viruses the —- may be left outside

Answer 13

capside

Question 14

uncoating

Answer 14

removal of the envelope and pr the capsid by host enzymes, sometimes within lysosomes (in eukaryotes)

Question 15

explain the mechanisms in which penetration may happen

Answer 15

1) naked viruses that have no envelope bind then inject their DNA inside the cell e..g bacteriophage
2) enveloped viruses bind then the 2 envelopes fuse together and that will be destroyed inside the host cell - frees the genome * viral glycoproteins remain in the cytoplasmic membrane
3) animal cells use endocytosis - the enveloped virus bind to the membrane and that will trigger endocytosis: the cell picks up the new thing in a new envelope so now the virus is in 2 membranes. they then get sent to the lysosome which degrade the capsid and the genome is released in the cytoplasm

Question 16

latent period

Answer 16

eclipse + maturation

Question 17

eclipse

Answer 17

time necessary for the host cells to replicate the viral genome and to synthesize the viral components

Question 18

maturation

Answer 18

time needed for the different components to be assembled

Question 19

release (rise period)

+mechanisms by which it can happen

Answer 19

• visions are detected outside the cell
• lysis: virus encoded proteins damage the cytoplasmic membrane. in bacteria, a virus encoded protein destroys the peptidoglycan layer
• budding: *enveloped viruses

Question 20

burst size

Answer 20

number of virions released

Question 21

how does release by budding occur

Answer 21

accumulation of the viral protein in the cytoplasm of the host cell –> the proteins result in a cluster of proteins in the membrane –> the viral capsid will bind there (underneath) and pushed through the membrane –> they fuse –> the virus is eventually released
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Question 22

most bacteriophages are —, and — ; some may possess envelopes

Answer 22

dsDNA, naked

Question 23

name the 2 types of bacteriophages

Answer 23

1) virulent phage: infection of host cells always leads to replication resulting in host cell lysis –> lytic pathway e.g. T4
2) temperate phage: have 2 options 1) lytic pathway 2) lysogenic pathway: becomes a prophage –> the genome of the virus will integrate the chromosome of the bacteria –> cell diviosn –> when nutrients are low (stationary phase) –> the virus gets out of the chromosome –> enters the lytic pathway e.g. lambda

Question 24

T4 adsorption

Answer 24

attaches to the core region of LPS by the tail fibres

Question 25

what happens after T4 adsorption

Answer 25

the tail sheet contracts, forcing the central core through the outer membrane. then tail lysozyme digest the peptidoglycan layer, forming a small pore. the phage DNA is the injected in to the cytoplasm of the host cell PAGE 14

Question 26

infection by temperate phage results in a:

Answer 26

prolonged latent state of infection (lysogeny)

Question 27

prophage

Answer 27

phage genome within the host cell chromosome

Question 28

lysogen

Answer 28

bacterium that contains the prophage

Question 29

explain the mechanisms in which lambda replicates

Answer 29

1) the phage genome is dsDNA and linear with cohesive ends 2) the ends cyclize together forming a circle 3) circle can be inserted into the genome at attgama - the enzyme lambda integrates catalyzes integration of the phage genome at this side

Question 30

where is lambda integrase encoded

Answer 30

on the phage genome

Question 31

classify phage MS2

Answer 31

ssDNA, plus strand

Question 32

SSDNA replication

Answer 32

minus strand must be synthesized fist by RNA replicase --> RNA depended RNA pol

Question 33

the genome of DNA viruses is usually replicated in the ----

Answer 33

nucleus

Question 34

the genome of RNA viruses is replicated in the ----

Answer 34

cytoplasm

Question 35

herpes is a ---- virus

Answer 35

DNA

Question 36

penetration of DNA genome viruses

Answer 36

fusion of the cell's cytoplasmic membrane with the virus envelope. nucleocapsid is transported to the nucleus where viral DNA is uncoated

Question 37

transcription/translation of DNA viruses

Answer 37

1) immediate early proteins: like transcription factors and in some cases virus specific RNA pol 2) delayed early proteins: viral specific DNA pol, and other viral proteins necessary for replication 3) late proteins: nucleocapsid

Question 38

assembly of DNA viruses occurs in the ----, envelope is added via a ----- process though the ---- membrane of the nucleus. the complete visions are the secreted out of the cell by ------ pathways

Answer 38

nucleus, budding, inner, ER Golgi

Question 39

name some examples of plus strand RNA viruses

Answer 39

coronavirus, poliovirus, hepatitis A

Question 40

in poliovirus, the plus strand RNA serves as a template for synthesis of ------. what does this do?

Answer 40

a large poly protein, cleaved not proteins --> each smaller subunit has a diff fxn 1) RNA replicase: relocated RNA of the virus first be making a negative strand that will be used to make more positive strand 2) structural proteins 3) proteins that help cleave the poly proteins (proteases)

Question 41

example of minus strand RNA viruses

Answer 41

measles, rabies, infleunza

Question 42

ssDNA minus strand replicaiton

Answer 42

the virion needs to have the RNA pol by itself so when it gets injected the minus strand becomes positive and gets replicated based on that

Question 43

example of dsDNA viruses

Answer 43

rotavirus

Question 44

what is retrovirus

Answer 44

RNA viruses examples include HIV - cancer causing viruses include: rous sarcoma virus - plus strand - ssRNA

Question 45

components of retrovirus

Answer 45

1) integrase 2) proteases 3) reverse transcriptase --> RNA dependent DNA pol that RNA --> DNA

Question 46

how does retrovirus enter the cell

Answer 46

ssRNA --> inserted into the cell --> virus gets inside the genome of the host like temperate bacteriophage --> in order to get instead into the genome it needs to get converted into DNA --> reverse transcription --> dsDNA genome version goes to the nucleus and gets instead --> the host can transcribe the genome into mRNA to make proteins

Question 47

consequences of viral infection in unicellular organisms

Answer 47

release of virions

Question 48

consequences of viral infection in multicellular organisms

Answer 48

1) cell death: following by the releases of visions via lysis 2) if release is slow --> budding of the virus through the membrane -- doesn't kill the cells --> called persistent infection: produces viruses slowly e.g. HIV 3) latent infection: the cell is infected same wth the genome but for some reason the virus is not replicated e.g. herpes (infected but not replicated) ** may lead to lysis 4) transformation into tumor cells 5) cell fusion

Question 49

cell fusion results in ------ that have ------ ------ and are usually ---- lived

Answer 49

hybrid cells, chromosomal aberration, short

Question 50

fusion often occurs in ----- viruses

Answer 50

enveloped

Question 51

cell fusion between the infected cell and another releases ----

Answer 51

nucleocapsids

Question 52

transformation

Answer 52

a cell that has acquired immortality, characterized by uncontrolled replication.

Question 53

T/F | both DNA and RNA viruses are known to cause tumours in animals and humans

Answer 53

true

Question 54

name the 4 different mechanisms by which transformation happens

Answer 54

1) transduction 2) insertion of a strong promoter 3) inactivation of a tumor suppressor gene 4) expression of a viral protein that induces transformation (DNA virus) - go over each in your notes