Viruses

Question 1

Identification

What is the first discovered virus? Who discovered it?

Answer 1

Tobacco Mosaic Virus (TMV)
Dmitri Ivanovsky

Question 2

Define

What is a virus?

Answer 2

• obligatory intracellular parasites

Extra
* macromolecular aggregates
* composed of inanimate particles that by themselves, cannot reproduce, metabolize, or carry functions associated with life.

Question 3

Explain

Are viruses alive?

Answer 3

It depends!
* Outside hosts: virion, inert/inactive
* Once they enter the body, they begin to display the characteristics of life (reproduction, evolution)

Question 4

Identification

Virus particle when found outside hosts

Answer 4

Virion

Question 5

List

Viral characteristics

4

Answer 5

1. Has a nucleic acid that functions as their genome (DNA or RNA)
2. Has a capsid: Protein coat/shell that encloses genome
3. Capsid can be enclosed within an outer envelope made up of lipids, proteins, and carbohydrates and taken from the host cells
4. Have surface proteins along its surface

Question 6

Identification

subunits that compose capsid

Answer 6

Capsomeres

Question 7

Identification

capsid + viral genome (DNA/RNA)

Answer 7

nucleocapsid

Question 8

Identification

• allows virus to interact with receptor proteins in their host cell → leads to infection
• determine the virus targets since they interact with specific receptors on the surface of their host cells

Answer 8

surface proteins

Question 9

Identification

What is the spike in SARS-Cov-2 (causes COVID-19)?

Answer 9

Spike glycoproteins

Question 10

Identification

In SARS-Cov-2 (causes COVID-19), what enzyme does its spike bind to?

Answer 10

angiotensin converting enzyme 2 (ACE2)

Question 11

Identification

What are the 4 key characteristics for viral classification?

according to the video

Answer 11

1. Genetic material
2. Target host
3. Capsid shape
4. Enzymes they produce

Question 12

Explain

What is the difference between an enveloped vs a naked virus?

Answer 12

Enveloped virus: nucleocapsid + outer envelope + spikes + surface proteins that help virus adhere to host

Naked virus: nucleocapsid + surface proteins

Question 13

Identification

What is the virus with the most base pairs? How many base pairs does it have?

Answer 13

Pandoravirus, 2.74M base pairs

Question 14

List

What are the different characteristics of the genetic material in a virus?

3

Answer 14

1. Single-stranded/Double-stranded
2. Linear/Circular/Segmented (Arrangement)
3. Plus Sense/Minus Sense

Question 15

T/F [Bonus: If false, what is wrong?]

In viruses, DNA can be single-stranded.

Answer 15

True
Although DNA is usually attributed as double-stranded, it can be single-stranded too.

Note: RNA can ONLY be single-stranded

Question 16

List

How can viruses be arranged? What are these arrangements similar to?

3

Answer 16

• Linear: like humans
• Circular: like bacteria
• Segmented: Unique to Influenza

Question 17

Explain

Why is influenza hard to kill?

Answer 17

Can escape antibodies after vaccination bc nucleic acids mutate a lot

Question 18

List

What processes does influenza undergo that makes them stronger?

3

Answer 18

Antigenic drift
* accumulation of mutations
* Change arrangement of RNA → new strain

Antigenic shift
* 2 influenza viruses are on 1 individual
* RNA of 2 viruses mix

Alters surface proteins → become undetectable by present antibodies

Question 19

Explain

How does a plus sense virus turn into viral proteins?

Answer 19

same base sequence as viral mRNA → translation → viral proteins

Question 20

Explain

How does a minus sense virus turn into viral proteins?

Answer 20

Viral replication: complementary to viral mRNA → conversion → plus sense RNA counterpart → translation → viral proteins

Question 21

Identification

What is a plus sense virus that goes through a different process?

Answer 21

Family Retroviridae

Question 22

Explanation

How does the Family Retroviridae convert the virus to viral proteins?

Answer 22

plus sense single stranded RNA → reverse transcription → DNA → transcription → mRNA → translation → viral proteins

Question 23

Identification

What virus has the smallest size?

Answer 23

Polio virus (28 nm, around the size of a ribosome)

Question 24

Identification

What virus has the largest size?

Hint: It is so big that it can be viewed under a light microscope

Answer 24

Pithovirus

Question 25

# List What are the kinds of capsid shape? What symmetry do they have? | 3

Answer 25

1. **Helical**: rod-shaped symmetry 2. **Icosahedral**: spherical symmetry 3. **Complex**: Head + tail bacteriophages

Question 26

# Identification 1. capsid shape with **rod-shaped symmetry** 1. Length: genome length 1. Width: Capsomere arrangement length 1. Ex.: Tobacco Mosaic virus, Ebola virus, Rabies virus

Answer 26

helical

Question 27

# Identification * capsid shape with spherical symmetry * **20 triangular faces, 12 corners** * Ex. poliovirus, herpes, influenza; many plant, animal, bacterial viruses

Answer 27

icosahedral

Question 28

# Identification * capsid shape with Head + tail bacteriophages * **Icosahedral head** * **Helical tail** * Ex. T4 bacteriophage

Answer 28

Complex viruses

Question 29

# List What kinds of assembly do viruses go through? | 2

Answer 29

1. **Self-assembly**: assembly info is in their genomes 1. **Assisted assembly**: need assistance of host cell’s chaperone proteins

Question 30

# List What are the subviral particles that cause disease? | 2

Answer 30

viriods, prions

Question 31

# Identification * Naked, single-stranded, cirular RNA with hairpin shaped structures * enters through a wound bc it can't interact w/ host cell receptors * attributed to severall plant diseases

Answer 31

Viroids

Question 32

# Identification Give an example of a viroid disease. What kind of symptoms do viroid diseases produce? | ____ related symptoms

Answer 32

Cadang-cadang disease, growth related symptoms

Question 33

# Explain How do viroids infect the host?

Answer 33

1. enters through a **wound** 2. relies on **host cell machinery** to replicate 3. moves across cells through **plasmodesmata** Extra: they usually *mimic or interfere* with host regulatory RNAs that function for growth

Question 34

# Identification How viroids move from one cell to another

Answer 34

plasmodesmata

Question 35

# Identification * **cause transmissible spongiform encephalopathies** which are uncurable neurodegenerative diseases * no DNA or RNA * can destroy the brain & other nervous tissue

Answer 35

Prions

Question 36

# Identification What does prions stand for?

Answer 36

proteinaceous infectious particles

Question 37

# Explain What is the mechanism of prions?

Answer 37

1. Prion host cells (ex. Human cells) have Prion Protein **(Prnp - gene)** 1. When Prnp is expressed → prion protein cellular **(PrPC - protein)** 1. Prion Protein Scrapie (**PrPSc** - Pathogenic Prion) enters body → **more PrPC becomes PrPSc** by misfolding 1. **Amyloid** formation 2. Leads to **transmissible spongiform encephalopathies** (Alzheimer's, Huntington’s, Parkinson’s, Type II Diabetes)

Question 38

# Identification * uncurable neurodegenerative diseases * what prions are responsible for

Answer 38

transmissible spongiform encephalopathies

Question 39

# Identification * insoluble crystalline fibers * what prions form * causes transmissible spongiform encephalopathies

Answer 39

amyloids

Question 40

# Fill in the blank Viroids are ____ that cause ____ diseases in ____, while Prions are ____ that cause ____ diseases in ____.

Answer 40

RNA, growth-related, plants proteins, neurodegenerative (nervous tissue related), animals