6.5: Viral Multiplication in Animal Viruses

Question 1

Multiplication cycles in animal cells

Answer 1

adsorption, penetration/uncoating, synthesis, assembly, and release

Question 2

How long does viral multiplication last?

Answer 2

8 to 36 hours

Question 3

What is adsorption

Answer 3

when a virus attaches to the specific glycoprotein receptor sites of a host cell

Question 4

Adsorption examples (2)

Answer 4

rabies virus attaches to ACH receptors of nerve cells, and HIV attaches to CD4 protein in WBCS

Question 5

What is host range

Answer 5

In adsorption when the range of hosts cells is limited due to needing a specific host molecule

Question 6

Host range examples (2)

Answer 6

Hepatitis B can only infect human liver cells, Poliovirus infects intestinal and nerve cells in primates

Question 7

What cells aren’t affected by adsorption?

Answer 7

One with compatible receptors

Question 8

What is a virus’s tropism?

Answer 8

Its capacity to infect certain groups of cells

Question 9

Two methods of animal viruses using penetration/uncoating?

Answer 9

Endocytosis and fusion into the cell, then uncoating of the capsid into the host

Question 10

Endocytosis example

Answer 10

Herpesvirus

Question 11

Fusion example

Answer 11

influenza and mumps virus

Question 12

What is synthesis

Answer 12

When a virus takes hold of the host’s genetic material and metabolism

Question 13

What are the two main variations in synthesis?

Answer 13

DNA viruses (minus poxvirus) are replicated and assembled in the nucleus, where RNA viruses are replicated and assembled in the cytoplasm

Question 14

RNA synthesis step 1

Answer 14

upon entry the viral nucleic acid starts to synthesize building blocks for new viruses and the +ssRNA gets translated into viral proteins

Question 15

RNA synthesis step 2

Answer 15

the +RNA is replicated into host machinery and then to -RNA which is the template for the create of new +RNAs which are the viral genomes of a new virus

Question 16

RNA synthesis step 3

Answer 16

additional RNAs are synthesized and proteins needed to make capsids, spikes, and viral enzymes are made in the ribosomes

Question 17

DNA synthesis step 1 (early phase)

Answer 17

viral DNA enters the nucleus and transcribes some mRNA which goes to the cytoplasm and gets translated into viral proteins for DNA replication in the nucleus (uses host cells polymerase)

Question 18

DNA synthesis step 2 (late phase)

Answer 18

other parts of viral DNA are made onto proteins to build the capsid and other structures and assembled into mature capsules that are released by budding or integration

Question 19

Double stranded DNA in synthesis…

Answer 19

acts directly on the DNA of the host cell and integrates with it, this can lead to transformation of the host into a cancer cell or tumor

Question 20

What is assembly

Answer 20

when the mature virus is being built in parts

Question 21

Assembly order of building

Answer 21

capsid is laid down to house the nucleic acid; viral spikes are inserted into the host cell’s membrane to pick up the virus after it buds off

Question 22

What happens during release

Answer 22

non-enveloped/complex viruses leave via cell lysis or rupture and enveloped cells leave via budding or exocytosis

Question 23

Describe budding

Answer 23

The nucleocapsid binds with the membrane and buds off, letting them shed without destruction

Question 24

Factors that influence release of a number of viruses

Answer 24

size of the virus and health of the host cell

Question 25

A single cell infected by poxvirus will release

Answer 25

around 3-4 thousand virions

Question 26

Release of virions has what potential

Answer 26

A great potential for viral proliferation

Question 27

What are cytoplasmic effects

Answer 27

virus induced damage to the cell that alters its appearance by changing shape, size, or changes intracellular

Question 28

What is a common cytoplasmic effect?

Answer 28

Finding inclusion bodies of viruses or damaged cell organelles in the cell

Question 29

What are cytoplasmic effects good for?

Answer 29

They can help with diagnosis, one example is when syncytia stops viruses form fusing to the membrane (called respiratory syncytial virus)

Question 30

Cytopathic effect in Poliovirus

Answer 30

Cells are killed completely

Question 31

Cytopathic effect in adenovirus

Answer 31

cells clump together and partially detach from the surface

Question 32

Cytopathic effect in rabies

Answer 32

inclusion bodies called negri bodies accumulate in the cytoplasm

Question 33

What are persistent infections

Answer 33

When a virus doesn't kill the host cell and becomes a provirus; roseola and measles

Question 34

What are proviruses in a chronic latent state?

Answer 34

Types of viruses that remain dormant and become reactivated; herpes simplex and zoster viruses

Question 35

How do viruses cause cancer?

Answer 35

When the virus goes under transformation and permanently alters the host's genetic material; called oncogenic

Question 36

Percentage of cancers caused by viruses?

Answer 36

13% but higher in developing countries

Question 37

What are ways a virus that can cause cancer can act in animal cells?

Answer 37

Directly carry the gene to cause cancer; induce a loss of growth regulation in the cell; cause uncontrolled growth or alterations

Question 38

What are oncoviruses

Answer 38

Viruses that can induce mammalian tumors; HPV with cervical cancer, herpes with Burkitt's lymphoma, hepatitis b and liver cancer

Question 39

What is HTLV-1?

Answer 39

An oncovirus involved in human leukemia

Question 40

What is a bacteriophage

Answer 40

a parasitic virus that engulfs a bacterial host cell that is very pathogenic; every bacterial species is parasitized by at least one

Question 41

Adsorption in bacteriophages

Answer 41

precise attachments using tail fibers

Question 42

penetration in bacteriophages

Answer 42

injection of nucleic acid through the cell walls, no need for uncoating

Question 43

synthesis and assembly in bacteriophages

Answer 43

in the cytoplasm; new DNA/RNA is replicated and synthesized, viral components synthesized, and cessation of host cell synthesis occurs

Question 44

release in bacteriophages

Answer 44

when the cell lyses due to enzymes slowly breaking it down

Question 45

Bacteriophage structure

Answer 45

mostly double stranded DNA, can have single RNA/DNA; complex capsid with icosahedral head full of DNA, a central tube, base plate, collar, tail pins, and fibers

Question 46

bacteriophage example

Answer 46

E. Coli, t-even

Question 47

What is lysogeny

Answer 47

an evolutionary advancement of the presence of a bacteriophage's DNA in a host cell without undergoing lysis

Question 48

What is a temperate host

Answer 48

the bacteriophage's DNA enters a cell but does not undergo synthesis or replication

Question 49

What is a prophage stage

Answer 49

when the host cell's chromosome has the bacteriophage DNA but is not undergoing lysis

Question 50

What is induction

Answer 50

when a prophage is triggered to start viral replication and synthesis

Question 51

What percent of bacterial DNA is estimated to be prophage DNA?

Answer 51

10-20%

Question 52

What is a viriophage

Answer 52

a virus that can parasitize another virus

Question 53

What is lysogenic conversion

Answer 53

when a bacterium gets a new genetic trait from its infecting agent

Question 54

Example of lysogenic conversion

Answer 54

Diphtheria, the lysogenic conversion releases the toxin that is harmful

Question 55

What is bacterial transduction

Answer 55

when phages transport genetic info from one bacterium to another