Unit 2 Viruses Flashcards Preview

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Flashcards in Unit 2 Viruses Deck (64):
1

The study of viruses

Virology

2

Do viruses only affect humans?

No.

3

Viralogy began as a science in the late 1800s when infectious tobacco mosaic virus was isolated in a filtered, bacteria-free fluid by

Ivanovski then Beijerinck

4

This person showed that a human disease called yellow fever was causes by a virus transmitted by mosquitoes

Walter Reed

5

What did Walter Reed use to filter liquids and trap cellular life?

What did he find

Membrane Filter

Infectious particles still got through the pores and were in the liquid

6

This term means that viruses are NOT cells. The need a living host to go inside of, and changes to its genome happen over time

intracellular obligate parasites

7

Are viruses alive?

What is the only property of being alive they have?

No

They have a genome that changes and evolves

8

The genome of viruses is so small that it needs to use the enzymes/materials of the host cell. What range of meters are viruses in? Bacteria?

Viruses: nm

Bacteria: um

9

This virus is an exception to the normal size, it is a virus of marine single-celled organisms and has a 730kbp genome

This one has a genome of over 1.2 megabase pairs that encodes 1,200 proteins

This one can be 400nm in diameter, witha 1.2 megabase pair genome coding for 979 proteins

CroV

Megavirus chilensis

Mimivirus

10

Viruses can be made or DNA OR RNA. Not both. This supports the RNA world hypothesis.

Most viruses are _________

Double stranded DNA

Note: some single stranded DNA, some single stranded RNA, some double stranded DNA

11

This is a protein shell around the viral genome that is composed of many capsomere proteins

Is it possible to have more than one?

Nucleocapsid

Yes with a large genome

12

The viral capsid and genome together are called the

nucleocapsid

13

It is possible for viruses to have an envelope. It can also be considered a

Where does it come from some times?

Plasma membrane

The PM/nuclear membrane/ER of the former host

14

Is the nuclear envelope similar to PMs we've learned about previously?

No.

15

Why do influenza and HIV have viral envelopes?

It allows them to attach to surfaces and infect host cells

16

For infection to occur with HIV and influenza, it must be in what type of environment?

Aqueous

17

All segmented viruses must be

Enveloped

18

Capsids often exhibit either ___ or _____ shapes

Helical or icosahedral

19

This type of capsid viral symmetry is spiral, where capsomeres spiral around like a paper towel roll, it is hollow at the center, and is like a rigid rod

Does it have a nuclear envelope?

Helical

Not if its a rigid rod.

20

This type of capsid viral symmetry looks circular but is actually made of repeating triangles

Does the amount of triangles change if the size of the genome changes?

Icosahedral

No, the triangles just get larger

21

What type of viral symmetry does influenza have?

What distinguishes it from other versions of these structures?

How many segments are there in its genome?

What is a segment?

Helical

It has flexible rods because it has a envelope

8 segments.

A segment of RNA with its own capsid.

22

What type of structures are HA and NA? They are located in the envelope of viruses

Spike Proteins

23

Influenza comes with its own _________ that is used to replicate the genome inside of a host cell

Viral Polymerase

24

The influenza virus is what type of shape?

Why is it complex?

This structure binds it to the cell wall of other cells and causes shape chang, like a hypodermic needle, to cause injection of a material

Complex

It doesn't fit neatly into helical or icosahedral

Tail fibers

25

If a plasma membrane surrounds the nucleocapsid, the virus ______

If there is no plasma membrane, its

enveloped

Naked

26

What does the acronym APUSSAE stand for?

What does it represent?

Adhere
Penetrate
Uncoat
Synthesis
Synthesis
Assembly
Exit

What must occur in the viral replication cycle

27

What do naked and enveloped viruses each use to stick to host?

What do they bind to?

Enveloped - spike proteins

Naked - Capsid proteins

They bind to surface receptors on the host cell

28

What is arguably the most important part in the viral replication cycle?

Entry (penetrate)

29

Mechanisms for entry vary depending upon the host cell

What do plant, fungal, and bacterial viruses have to contend with that animal viruses don't?

A cell wall structure

30

What is the process that a non-enveloped virus uses to enter a host animal cell?

What is the example virus used in lecture?

Endocytosis

Rhinovirus

31

In the first step of endocytosis of a non-enveloped virus, the virus attaches to the ________

In the second step, endocytosis is initiated.
In the third step, a _______ forms with the virus inside
In the 4th step, the _____ escapes into the cytoplasm and uncoats to release the genome

Cell receptor

Endosome

Nucleocapsid

32

What are the two methods by which enveloped viruses can enter into a host animal cell?

Membrane fusion

Endocytosis

33

What virus is used as the example virus in membrane fusion of an enveloped virus?

In the first step, the virus attaches to the _____
In the second step, a _________ in the attachment protein and bound receptor initiates membrane fusion.
In the third step, the viral envelope fuses with the _______
In the 4th step, the ______ enters the cytoplasm and uncoats to release the genome

HIV

Conformational Change

Plasma Membrane

Nucleocapsid

34

What virus is used as the example virus in endocytosis of an enveloped virus?

In the first step, the virus attaches to the _____
In the second step, ______ is initiated
In the third step, a _____ forms with the virus inside
In the fourth step the _____ of the endosome initiates fusion of the viral envelope with the endosome membrane. Nucleocapsids are released

Influenza

Cell receptor
Endocytosis
Endosome
low pH

35

Entry into plant cells often depends upon some damage to the plant tissues to open a spot in the

ex) insect feed, wind damage, hail/rain damage, fire damage, human induced damage

Cell wall

36

For viral entry into bacterial cells, during the first step _____ attach to cell receptors
In the second step, _______ in tail fibers bring the base of the tail in contact with the host cell surface
In the third step, rearrangement of tail proteins allow inner core __________ to extend down into the cell wall
In the fourth step, contact with the PM initiates transfer of DNA through a pore formed in the _____

Tail Fibers

Conformational Change

Tube Proteins

Lipid Bilayer

37

During entry into bacterial cells, what makes the hole/cuts into the peptidoglycan area?

Which molecule does it come from?

Lysozyme

It is coded by the viral genome

38

The evolutionary history of viruses isn't clear, but what 3 hypotheses have emerged/

Coevolution
Regressive
Progressive

39

This hypothesis of the origin of viruses states that viruses evolved along with their host cells. It is evidenced by the fact the RNA viruses code their own polymerase so that they can persist inside of DNA cells today

This could explain the origin of many ___ viruses

Is there much supporting evidence for this?

Coevolution hypothesis

RNA viruses

No

40

This hypothesis of the origin of viruses states that viruses are cells that lost some of the replicative and metabolic traits over time

An example of this is that there are some _____ that have no mitochondria, as they have no metabolism because they parisitize other organisms

What doesn't this explain?

Regressive Hypothesis

Protozoa

RNA viruses

41

This hypothesis of the origin of viruses states that existing genetic elements gradually gained the ability to move from cell to cell

What provides evidence for this theory?

Progressive Hypothesis

Transposons and retrotransposons

42

This is also called a jumping gene and is a segment of DNA that cuts itself out and reinserts into somewhere else, evidence of the progressive theory

This is a segment of DNA copied into mRNA, converted by an enzyme back to DNA, and put into DNA in a new position

Transposon

Retrotransposon

43

What enzyme converts the RNA form of retrotransposons back the DNA?

What is one example of a retrovirus?

Reverse Transcriptase

HIV

44

Are viruses trickier to work with than bacteria?

Why?

Yes.

They are small and replicate only within appropriate host cells. Also they can't be seen by the naked eye

45

There are two types of bacteriophages, what are they?

This type will replicate inside of and burst open (lyse) the host cells

This tape can integrate its genome into the host cell genome (becoming a prophage) and be replicated each time the host cell replicates

Lytic and lysogenic

Lytic

Lysogenic

46

Which type of bacteriophage occurs temporarily?

Under what circumstances does it get pushed back to the other cycle?

Lysogenic

Lack of nutrients or UV light, aka poor growth conditions

47

If a culture of bacteria is infected with a bacteriophage and the cloudiness of the vial starts to disappear, what type of bacteriophage is it?

Lytic, the bacteria are dying

48

What are plaques on a nutrient agar base indicative of?

A clear plaque is

A cloudy plaque is

Bacterial cell death

Lytic

Lysogenic (some cells are still alive)

49

What was the breakthrough in modern virology that allowed more rigorous study of viruses?

What two things are necessary for tissue culturing?

Tissue Culturing

Nutrients and sterility

50

The tools for animal virus cultivation helped develop the first human cell line, known as

HeLa cells

51

Changes that occur in cells due to a cultured virus that can be observed

Why must everything be sterile in this circumstance?

Cytopathic Effects

To make sure that only the virus is acting on the cells

52

Historically, the names of virus have been uniform or varied?

Varied

53

What is the current method of viral classification?

What do the letters stand for?

What do they classify viruses based upon?

ICTV

International Committee on Taxonomy of Viruses

Order, Family, Subfamily, Genus, Species (this method is familiar to people)

54

Another method that was developed based around mRNA production methods

How many classes does it separate viruses into?

Baltimore Classification System

Seven

55

This type of RNA can act right away to react with ribosomes and code for proteins

This type of RNA has to be changed into a complimentary strand first.

Positive Sense RNA

Negative Sense RNA

56

The first step in the identification of viruses rests on observations of

Is this method infallible?

morphology

Nope.

57

What is the best method of viral identification?

What methods are used for it?

What does it specifically study and look for?

Nucleic Acid Analysis

PCR and reverse-transcriptase PCR

Viral evolution patterns

58

These pathogens are simpler than viruses and consist only of naked RNA, are extremely small (about 400 nucleotides) and have a high degree of internal complementarity.

They are resistant to

Why?

Where have they only been observed to cause disease?

Viroids

Ribonucleases

They don't fit into ribozymes

Plants

59

This type of virus like particle requires a helper virus for its replication, and carries its own capsid protein gene

What are the examples given in lecture

Satellite Viruses

Hepatitis D, HDV

60

These virus like particle require a helper virus for replication BUT require the capsid protein from the helper virus

Satellite RNAs

61

These are proteinaceous infectious particles that lead to transmissible spongiform encephalopathies, like mad cow disease

Prions

62

What makes prions particularly dangerous in Mad Cow and ground beef?

Heating denatures DNA and RNA but not protein structures

63

What does prion do to proteins?

What symptoms show in mad cow?

If its note caught before slaughtering, the disease spreads.

Also deer in WI and MI have prions

Cause the proteins to form a prion shape, leading to death of neurons

holes in brain, sponge like

64

Note: spontaneous prion diseases have formed, though very rare, possibly because of

genetic mutation