Unit 2 Viruses

Question 1

The study of viruses

Answer 1

Virology

Question 2

Do viruses only affect humans?

Answer 2

No.

Question 3

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

Answer 3

Ivanovski then Beijerinck

Question 4

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

Answer 4

Walter Reed

Question 5

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

What did he find

Answer 5

Membrane Filter

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

Question 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

Answer 6

intracellular obligate parasites

Question 7

Are viruses alive?

What is the only property of being alive they have?

Answer 7

No

They have a genome that changes and evolves

Question 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?

Answer 8

Viruses: nm

Bacteria: um

Question 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

Answer 9

CroV

Megavirus chilensis

Mimivirus

Question 10

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

Most viruses are _________

Answer 10

Double stranded DNA

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

Question 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?

Answer 11

Nucleocapsid

Yes with a large genome

Question 12

The viral capsid and genome together are called the

Answer 12

nucleocapsid

Question 13

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

Where does it come from some times?

Answer 13

Plasma membrane

The PM/nuclear membrane/ER of the former host

Question 14

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

Answer 14

No.

Question 15

Why do influenza and HIV have viral envelopes?

Answer 15

It allows them to attach to surfaces and infect host cells

Question 16

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

Answer 16

Aqueous

Question 17

All segmented viruses must be

Answer 17

Enveloped

Question 18

Capsids often exhibit either ___ or _____ shapes

Answer 18

Helical or icosahedral

Question 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?

Answer 19

Helical

Not if its a rigid rod.

Question 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?

Answer 20

Icosahedral

No, the triangles just get larger

Question 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?

Answer 21

Helical

It has flexible rods because it has a envelope

8 segments.

A segment of RNA with its own capsid.

Question 22

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

Answer 22

Spike Proteins

Question 23

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

Answer 23

Viral Polymerase

Question 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

Answer 24

Complex

It doesn’t fit neatly into helical or icosahedral

Tail fibers

Question 25

If a plasma membrane surrounds the nucleocapsid, the virus ______ If there is no plasma membrane, its

Answer 25

enveloped Naked

Question 26

What does the acronym APUSSAE stand for? What does it represent?

Answer 26

``` Adhere Penetrate Uncoat Synthesis Synthesis Assembly Exit ``` What must occur in the viral replication cycle

Question 27

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

Answer 27

Enveloped - spike proteins Naked - Capsid proteins They bind to surface receptors on the host cell

Question 28

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

Answer 28

Entry (penetrate)

Question 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?

Answer 29

A cell wall structure

Question 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?

Answer 30

Endocytosis Rhinovirus

Question 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

Answer 31

Cell receptor Endosome Nucleocapsid

Question 32

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

Answer 32

Membrane fusion Endocytosis

Question 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

Answer 33

HIV Conformational Change Plasma Membrane Nucleocapsid

Question 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

Answer 34

Influenza Cell receptor Endocytosis Endosome low pH

Question 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

Answer 35

Cell wall

Question 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 _____

Answer 36

Tail Fibers Conformational Change Tube Proteins Lipid Bilayer

Question 37

During entry into bacterial cells, what makes the hole/cuts into the peptidoglycan area? Which molecule does it come from?

Answer 37

Lysozyme It is coded by the viral genome

Question 38

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

Answer 38

Coevolution Regressive Progressive

Question 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?

Answer 39

Coevolution hypothesis RNA viruses No

Question 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?

Answer 40

Regressive Hypothesis Protozoa RNA viruses

Question 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?

Answer 41

Progressive Hypothesis Transposons and retrotransposons

Question 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

Answer 42

Transposon Retrotransposon

Question 43

What enzyme converts the RNA form of retrotransposons back the DNA? What is one example of a retrovirus?

Answer 43

Reverse Transcriptase HIV

Question 44

Are viruses trickier to work with than bacteria? Why?

Answer 44

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

Question 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

Answer 45

Lytic and lysogenic Lytic Lysogenic

Question 46

Which type of bacteriophage occurs temporarily? Under what circumstances does it get pushed back to the other cycle?

Answer 46

Lysogenic Lack of nutrients or UV light, aka poor growth conditions

Question 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?

Answer 47

Lytic, the bacteria are dying

Question 48

What are plaques on a nutrient agar base indicative of? A clear plaque is A cloudy plaque is

Answer 48

Bacterial cell death Lytic Lysogenic (some cells are still alive)

Question 49

What was the breakthrough in modern virology that allowed more rigorous study of viruses? What two things are necessary for tissue culturing?

Answer 49

Tissue Culturing Nutrients and sterility

Question 50

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

Answer 50

HeLa cells

Question 51

Changes that occur in cells due to a cultured virus that can be observed Why must everything be sterile in this circumstance?

Answer 51

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

Question 52

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

Answer 52

Varied

Question 53

What is the current method of viral classification? What do the letters stand for? What do they classify viruses based upon?

Answer 53

ICTV International Committee on Taxonomy of Viruses Order, Family, Subfamily, Genus, Species (this method is familiar to people)

Question 54

Another method that was developed based around mRNA production methods How many classes does it separate viruses into?

Answer 54

Baltimore Classification System Seven

Question 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.

Answer 55

Positive Sense RNA Negative Sense RNA

Question 56

The first step in the identification of viruses rests on observations of Is this method infallible?

Answer 56

morphology Nope.

Question 57

What is the best method of viral identification? What methods are used for it? What does it specifically study and look for?

Answer 57

Nucleic Acid Analysis PCR and reverse-transcriptase PCR Viral evolution patterns

Question 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?

Answer 58

Viroids Ribonucleases They don't fit into ribozymes Plants

Question 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

Answer 59

Satellite Viruses Hepatitis D, HDV

Question 60

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

Answer 60

Satellite RNAs

Question 61

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

Answer 61

Prions

Question 62

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

Answer 62

Heating denatures DNA and RNA but not protein structures

Question 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

Answer 63

Cause the proteins to form a prion shape, leading to death of neurons holes in brain, sponge like

Question 64

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

Answer 64

genetic mutation